세포분열Cell division--*체세포분열Mitosis/ 감수분열Meiosis***"RiboNucleic Acid…
페이지 정보
본문
Cell biology Metabolism 세포 생화학 반응--세. 포는 대사작용을 통해 에너지와 환원력을 만들고 세포를 구성하는 고분자 물질
====
인체를 구성하는 세포들은 크기도 제각각이다. 가장 작은 적혈구(지름 7~8μm)와 가장 큰 골격근 세포(지름 100μm, 길이 2~3cm) 차이는 100만배가 넘어, 땃쥐와 대왕고래의 몸집 차이와 비슷하다.Sep 26, 2023
작을수록 많고 크면 적다…인체 세포도 '크기와 수 반비례법칙'
====
Cell Size - 4.2: 세포 크기
세포의 크기는 유기체 마다, 또 같은 유기체 사이에서도 매우 다양합니다. 예를 들어 가장 작은 박테리아는 직경이 0.1마이크로미터(μm)이며, 대부분의 진핵 ...
[장수철의 생물학을 위하여] 세포의 크기
서울신문
Dec 11, 2018 — 세포는 지름이 0.01~0.1㎜ 정도이다. 결국 코끼리, 버섯, 거미가 크기가 다른 것은 세포의 수가 다르기 때문이다. 코끼리는 세포 수가 거미보다 많다는 말이다.
[기초]세포의 모양과 크기
Jun 20, 2005 — 하지만 대부분의 진핵 세포는 직경이 10μm -1백μm 사이다. (1) 진화는 세포의 크기를 작게 유지하면서 개체 크기의 증가를 조절하기 위해 세포의 수를 ...
====
Cell biology is the study of cell structure and function, and it revolves around the concept that the cell is the fundamental unit of life.
Cell Biology | Learn Science at Scitable - Nature
https://www.google.ca/search?q=cell+biology&sxsrf=AB5stBidukaXPR_702kfNc_zLbruKeTqew%3A1690711776831&source=hp&ei=4DbGZOKvMM-80PEPw6K38As&iflsig=AD69kcEAAAAAZMZE8EyFDt5bgGJWUacnhDX6p-TC54gp&oq=&gs_lp=Egdnd3Mtd2l6IgAqAggAMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnSJcNUABYAHABeACQAQCYAQCgAQCqAQC4AQHIAQCoAgo&sclient=gws-wiz
=======================
세포 생화학 반응
세포 안에서 일어나는 모든 생화학 반응을 일컬어 대사작용(metabolism)이라 한다. 세. 포는 대사작용을 통해 에너지와 환원력을 만들고 세포를 구성하는 고분자 물질 ...
=====================================-
(metabolism)
https://www.google.ca/search?q=metabolism&sxsrf=AB5stBiX-RaICXS8wj0BrJ38ul3R10X3lQ%3A1690712119801&source=hp&ei=NzjGZPuWLq_G0PEP__OXmA0&iflsig=AD69kcEAAAAAZMZGRzC_kiPYLT8Yxr1OWsU83szU0Xmb&oq=&gs_lp=Egdnd3Mtd2l6IgAqAggFMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnSL4jUABYAHABeACQAQCYAQCgAQCqAQC4AQHIAQCoAgo&sclient=gws-wiz
세포 생화학 반응
https://www.google.ca/search?q=%EC%83%9D%ED%99%94%ED%95%99%EB%B0%98%EC%9D%91&sxsrf=AB5stBhCuKcj8WnoQbFnJ44-5mVlosaXjg%3A1690711914023&source=hp&ei=aTfGZK2APPWt0PEPpO6msAo&iflsig=AD69kcEAAAAAZMZFek3YmJWOMZdNl2iztcUftjldZwjc&oq=&gs_lp=Egdnd3Mtd2l6IgAqAggBMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnSJkOUABYAHABeACQAQCYAQCgAQCqAQC4AQHIAQCoAgo&sclient=gws-wiz
==============
체세포분열(mitosis /maɪˈtoʊsɪs/; 유사분열)은 복제된 염색체가 두 개의 세포핵으로 분리되는 세포 주기의 한 부분이다. 세포 분열은 전체 염색체 수 ..
감수분열 - 위키백과, 우리 모두의 백과사전https://ko.wikipedia.org › wiki › 감...
감수분열(meiosis, Listen/maɪˈoʊsɪs/, 감소하는 분열이라는 점에서 그리스어로 줄어든다는 의미의 μείωσις, meiosis에서 유래함)이란 유성 생식을 하는 생물들이 정자 ...
https://ko.wikipedia.org/wiki/%EA%B0%90%EC%88%98%EB%B6%84%EC%97%B4
세포생물학에서 체세포분열(mitosis /maɪˈtoʊsɪs/; 유사분열)은 복제된 염색체가 두 개의 세포핵으로 분리되는 세포 주기의 한 부분이다. 세포 분열은 전체 염색체 수
https://ko.wikipedia.org/wiki/%EC%B2%B4%EC%84%B8%ED%8F%AC%EB%B6%84%EC%97%B4
======================================================================================...
cell theory
https://www.google.ca/search?q=cell+theory&tbm=isch&ved=2ahUKEwiu-qDyy7r8AhU6ADQIHUKACLUQ2-cCegQIABAA&oq=cell+&gs_lcp=CgNpbWcQARgJMgQIIxAnMgQIIxAnMgQIABBDMggIABCABBCxAzIICAAQgAQQsQMyCAgAEIAEELEDMggIABCABBCxAzIICAAQgAQQsQMyBQgAEIAEMgUIABCABFDODFjODGDLN2gAcAB4AIABpwWIAcMIkgEFNC0xLjGYAQCgAQGqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=fxa8Y-6-E7qA0PEPwoCiqAs
===============================================
cellhttps://www.google.ca/search?q=cell&dcr=0&sxsrf=ALeKk00-4ESN8NLPcmJvBgcC4zVvxHU00g:1610793365549&tbm=isch&source=iu&ictx=1&fir=jdQpUZ4xClUx4M%252CdHCEwQt_r3xVsM%252C_&vet=1&usg=AI4_-kQzXtRTAxxlgHz_fm3qoP1YTKqBAw&sa=X&ved=2ahUKEwjhj_DyoKDuAhUICTQIHcZNBkoQ_h16BAgMEAE#imgrc=jdQpUZ4xClUx4M
세포
생물의 구조적, 기능적 단위
세포는 모든 생물체의 구조적, 기능적 기본 단위이다. 세포에 대해 연구하는 학문을 세포생물학이라고 한다. 세포는 세포막으로 둘러싸인 세포질로 구성되어 있으며, 단백질 및 핵산과 같은 많은 생체분자들을 포함하고 있다. 생물은 단세포 생물 또는 다세포 생물로 분류할 수 있다. 식물 및 동물의 세포수는 생물종마다 다르며, 사람은 약 60조 개의 세포를 가지고 있…
Cell (biology) - Wikipedia
https://en.wikipedia.org/wiki/Cell_(biology)
The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and metabolites. The term comes from the Latin word cellula meaning … 더 보기
Cell types
Cells are of two types: eukaryotic, which contain a nucleus, and prokaryotic cells, which do not have a nucleus, but a nucleoid region is still present. Prokaryotes are single-celled organisms, while eukaryotes may … 더 보기
Cellular processes 이미지
Origins 이미지
Subcellular components
All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, regulates what moves in and out (selectively … 더 보기
Cellular processes
Replication
Cell division involves a single cell (called a mother cell) dividing into two daughter cells. This leads to growth in multicellular organisms (the … 더 보기
Multicellularity
Cell specialization/differentiation
Multicellular organisms are organisms that consist of more than one cell, in contrast to single-celled organisms.
In complex … 더 보기
Cell shape, also called cell morphology, has been hypothesized to form from the arrangement and movement of the cytoskeleton. Many advancements in the study of cell morphology come from studying simple bacteria such as Staphylococcus aureus 더 보기
Structures outside the cell membrane
Many cells also have structures which exist wholly or partially outside the cell membrane. These structures are notable because they are not protected from the external environment by the semipermeable cell membrane. In order to assemble these … 더 보기
Origins
The origin of cells has to do with the origin of life, which began the history of life on Earth.
Origin of the first cell 더 보기
CC-BY-SA 라이선스가 적용되는 Wikipedia 텍스트
원본: Wikipedia
=======================================
cell
https://www.google.ca/search?q=cell&dcr=0&sxsrf=ALeKk00-4ESN8NLPcmJvBgcC4zVvxHU00g:1610793365549&tbm=isch&source=iu&ictx=1&fir=jdQpUZ4xClUx4M%252CdHCEwQt_r3xVsM%252C_&vet=1&usg=AI4_-kQzXtRTAxxlgHz_fm3qoP1YTKqBAw&sa=X&ved=2ahUKEwjhj_DyoKDuAhUICTQIHcZNBkoQ_h16BAgMEAE
==================================
cell division
https://www.google.ca/search?q=cell+division&tbm=isch&ved=2ahUKEwiE58zRyrr8AhUOBDQIHZcrCLQQ2-cCegQIABAA&oq=cell&gs_lcp=CgNpbWcQARgJMgQIIxAnMgQIABBDMgcIABCxAxBDMgcIABCxAxBDMgcIABCxAxBDMggIABCABBCxAzIECAAQQzIHCAAQsQMQQzIFCAAQgAQyBwgAELEDEENQAFgAYNaIAmgAcAB4AIABhgKIAbwDkgEFMC4xLjGYAQCqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=LhW8Y4SYGI6I0PEPl9egoAs
=======================================
cell division stages
https://www.google.ca/search?q=cell+division+stages&tbm=isch&ved=2ahUKEwiRn8-Ly7r8AhUUMH0KHSbFAGUQ2-cCegQIABAA&oq=cell+division&gs_lcp=CgNpbWcQARgDMgQIIxAnMgQIIxAnMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgUIABCABDIECAAQQzIECAAQQ1AAWABg62hoAHAAeACAAbwCiAG8ApIBAzMtMZgBAKoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=qBW8Y5GrBJTg9AOmioOoBg
============================
cell division mitosis and meiosis
https://www.google.ca/search?q=cell+division+mitosis+and+meiosis&tbm=isch&ved=2ahUKEwiRn8-Ly7r8AhUUMH0KHSbFAGUQ2-cCegQIABAA&oq=cell+division&gs_lcp=CgNpbWcQARgEMgQIIxAnMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgUIABCABDIECAAQQzIECAAQQ1AAWABggY8CaABwAHgAgAFpiAGoAZIBAzEuMZgBAKoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=qBW8Y5GrBJTg9AOmioOoBg
=====================================================================================================
RiboNucleic Acid(리보핵산]-[mRNA(전령messenger설계]*[리보솜 Ribosomal RNA, rRNA합성] (Transter RNA tRNA운반체]
=============================================================================
3종류의 RNA:
전령 RNA(Messenger RNA, mRNA): 단백질의 설계도
리보솜 RNA(Ribosomal RNA, rRNA): 단백질 합성장소
운반 RNA(Transter RNA, tRNA): 아미노산의 운반체
=======================================
https://namu.wiki/w/%EC%83%9D%EB%AA%85
====================================
https://ko.wikipedia.org/wiki/%EC%83%9D%EB%AA%85#:~:text=%EC%83%9D%EB%AA%85(%E7%94%9F%E5%91%BD)%20%EB%98%90%EB%8A%94%20%EC%82%B6%EC%9D%80%20%EC%83%9D%EB%AC%BC,%ED%99%95%EC%8B%A4%EC%B9%98%20%EC%95%8A%EC%95%84%20%EA%B3%84%EC%86%8D%20%EB%85%BC%EC%9F%81%20%EC%A4%91%EC%9D%B4%EB%8B%A4.
================================
生命 / life
생물들이 가지고 있는 특성으로 생물이 살아서 숨쉬고 활동할 수 있게 하는 힘을 말한다. 생명력은 항상성을 포함한 여러가지 의미로 쓰인다. 생명에 대한 일반적인 과학적 정의는 생물 문서에 나와 있다. 또 다른 관점에서는 외부나 전체의 엔트로피 증가를 가속화하여 자신의 엔트로피를 낮추거나, 유지하는 개체로 보기도 한다. 이러한 주장은 에르빈 슈뢰딩거의 저서 '생명이란 무엇인가?'에서 제기된 것을 계기로 대중화되었으며 사회유기체설과도 관계가 있다. 인간을 비롯한 모든 생명은 죽으면 무기체로 돌아간다.
애시당초 생물이라는 것 자체가 분류의 하나이기에 생물학적인 관점에서도 아주 명확한 정의는 없다. 보통 아래의 특성을 전부 가지거나 대부분 가지고 있는 개체는 생명으로 본다.
1) 생식과 유전
2) 세포로 이루어짐
3) 물질대사
4) 자극에 대한 반응, 항상성
5) 적응과 진화
6) 발생과 생장
바이러스는 유전물질을 가지고 증식을 하여[2] 자연선택에 의한 진화도 하지만 물질대사[3]와 세포체 구조의 부족 때문에 일반적으로는 생명으로 간주되지 않는다
=====================================
생명
위키백과, 우리 모두의 백과사전.
생명(生命) 또는 삶은 생물이 태어나서 죽기 전까지의 과정 및 상태를 말하나 학술적으로 생과 사의 경계는 확실치 않아 계속 논쟁 중이다.
다양한 생물계 수준.
Magnify-clip.png
생물 분류의 계급의 주요 8개 순위. 사소한 중간 순위는 표시하지 않음. 밑으로 갈수록 더 좁은 범위의 계급.
생명의 정의
생명이란 자체 신호를 가지고 스스로를 유지할 수 있는 물체를, 그러한 기능이 종료되었거나 (죽음) 또는 그러한 기능이 없어 비활성체로 분류되었거나를 막론하고 그렇지 않은 것과를 구별짓는 특성이다. 생물학적으로 볼 때, 생명체는 다음과 같은 특성을 지니지만 엄밀하지는 않다.
물질대사에 바탕을 둔 정의
생장한다.
물질대사를 한다.
외부적으로나 내부적으로 움직인다.
자신과 닮은 개체를 생산해 내는 생식기능이 있다.
외부 자극에 반응한다.
위의 기준을 엄밀하게 적용한다면 다음과 같은 문제가 생긴다.
불이 살아있다고 할 수 있다.
노새는 생식 능력이 없으므로 살아있다고 할 수 없다.(그러나 노새의 세포 하나하나는 분열할 수 있다)
바이러스는 성장하지 않고 숙주세포 바깥에서는 생식을 할 수 없으므로 살아있다고 할 수 없다.
지구상의 생명체를 연구하는 생물학자들은 살아있는 생명체가 다음과 같은 현상을 보인다고 한다.
살아있는 생명체는 탄수화물, 지질, 핵산, 단백질과 같은 성분을 지니고 있다.
살아있는 생명체는 살아가기 위해 에너지와 물질을 모두 필요로 한다.
살아있는 생명체는 하나나 그 이상의 세포로 이루어져 있다.
살아있는 생명체는 항상성을 유지한다.
살아있는 생명체의 종은 진화한다.
지구상의 생명체는 모두 탄소로 이루어진 유기체로 이루어져 있다. 어떤 사람들은 이런 점이 모든 우주의 모든 생명체에도 해당한다고 보지만, 다른 이들은 이 현상을 '탄소 쇼비니즘'이라고 부른다.
살아있는 생명체는 호흡을 해야 한다
생화학적(분자생물학적) 정의
생물(生物): 생명이 있는 것
생물을 구성하는 생화학적 분자들
단백질
지방(지질, 지방산)
탄수화물
핵산(DNA, RNA)
효소반응: 단백질로 만들어진 생체 촉매
핵산
DNA
<nowiki /> 이 부분의 본문은 DNA입니다.
Deoxyribonucleic acid(디옥시리보핵산)
생명의 청사진
후손에게 전해지는 유전물질(예외: retrovirus)
Wiki letter w.svg 이 문단은 아직 미완성입니다.
RNA
대개 mRNA(messenger RNA)를 가리킴
Ribonucleic acid(리보핵산)
단백질 합성의 청사진
3종류의 RNA:
전령 RNA(Messenger RNA, mRNA): 단백질의 설계도
리보솜 RNA(Ribosomal RNA, rRNA): 단백질 합성장소
운반 RNA(Transter RNA, tRNA): 아미노산의 운반체
현대생물학의 기본 패러다임: 분자생물학
<nowiki /> 이 부분의 본문은 분자생물학입니다.
단백질의 효소와 생합성을 지배하는 디옥시리보핵산 또는 디엔에이(DNA)의 구조와 특성을 바탕으로, 중요한 생명현상을 설명하려는 생물학의 한 분야이다. 분자생물학의 발달은 1940년대에 DNA가 유전자의 본체임이 밝혀지고, 동시에 DNA의 유전정보가 RNA를 통하여 세포질 속에서 단백질 합성을 지배한다는 사실이 차츰 알려지게 되었다. 더욱이 1953년 J.D.웟슨과 F.H.C.크릭에 의하여 DNA의 이중나선구조의 모형이 제출됨에 이르러 새로운 단계를 맞이하였다. 그 후, 분자생물학의 주류는 DNA의 복제 및 단백질의 생합성을 중심으로 하여 유전의 본질 및 유전의 메커니즘을 설명하고, 나아가서 생물체의 조절작용이나 진화의 현상을 설명하는 것으로 되었다. 따라서, 분자생물학의 중심이 되는 것은 분자유전학으로 볼 수 있다. 그러나 근육의 기본이 되는 수축단백질인 액토미오신이라는 단백질의 분자구조를 바탕으로 근육의 수축운동을 설명한다든지, 뇌에 있어서의 기억의 기작을 단백질이나 RNA의 미세한 구조의 변화로 설명하려는 일 등도 분자생물학에 포함시키고 있다.
유전학적 정의
다윈의 <종의 기원>
<nowiki /> 이 부분의 본문은 종의 기원입니다.
영국의 생물학자 찰스 다윈(1809년~1882년)의 생물의 진화론에 관한 저서로서, 1859년 11월 런던의 존 머리사(John Murray社)에서 간행하였다. 다윈은 1858년 7월 1일 린네 학회에서 A.R.월리스와 함께 진화론의 논문을 발표하고 나서, 요약 형식으로 이 책을 간행하였다. 전문 14장으로 구성되고, 변이(變異)의 법칙·생존경쟁·본능·잡종(雜種)·화석(化石)·지리적 분포·분류학 및 발생학 등의 여러 면에서 자연선택을 전개하고 있다. 1872년에 간행된 제6판이 최종판인데, 이때 과학적으로 제기된 여러 이론(異論)에 답한 새로운 한 장(章)이 제7장으로 추가되었다.
W.페리의 자연신학(自然神學)의 토대였던 적응의 현상에 자연적 설명을 부여하려는 것이 이 책을 간행하게 된 목표 중의 하나였다. 간행 직후부터 종교계의 심한 공격을 받았으나, 약 10년만에 생물학계에서 확고한 지위를 획득하였다.
멘델의 유전법칙
<nowiki /> 이 부분의 본문은 멘델의 유전법칙입니다.
그레고어 멘델(G.J. Mendel)이 완두콩을 이용한 교배 실험을 통해서 밝혀낸 유전법칙. 1865년에 처음 발표되어 유전학을 만들어 내는 계기가 되었다 멘델 이전에는 유전 현상을 설명하기 위해서, 정자와 난자 속에 있는 액체가 섞여서 부모의 특징이 이어진다는 혼합 이론을 사용하였다. 이 이론에 대항하여 멘델은 부모의 특성, 즉 형질을 결정하는 것은 단위로 환원할 수 있는 물질이라는 것을 밝혀 냈다. 멘델 스스로는 여기에 따로 이름을 붙이지 않았지만 이것이 바로 유전자이다. 즉 멘델은 그의 법칙을 통해 유전자 개념을 처음 과학적으로 확립한 셈이다. 그러나 당초 1865년에 멘델이 처음 이 법칙을 발표했을 때에는 크게 주목 받지 못했다. 하지만 그 성과가 완전히 묻힌 것은 아니고, 다른 학자들의 논문에서도 멘델에 대한 언급을 볼 수 있었으며 1881년에 나온 브리태니커 백과사전에도 멘델의 연구가 소개되어 있었다. 그러다 1900년에 코렌스(C. Correns), 체르마크(E.V. Tschermak), 드 브리스(H. de Vries)가 유사한 연구를 하다가 동일한 시기에 멘델의 연구를 다시 발견하여 세상에 알려지게 되었다. 이 중에서 코렌스가 멘델의 연구 성과에 "멘델의 법칙"이라는 이름을 붙였다.
멘델의 연구
멘델은 자신의 연구를 위해서 완두콩을 그 재료로 사용했다. 우선 완두콩을 잘 키워서 키가 큰 완두콩과 키가 작은 완두콩을 서로 분리해 낸다. 이렇게 키가 큰 것과 작은 것이 각각 완두콩의 형질이 된다. 키가 큰 것은 큰 것대로 따로 키우고 작은 것은 작은 것대로 따로 키워서, 몇 세대 후에는 무조건 키가 큰 종자와 무조건 키가 작은 종자를 얻는다. 이 완두콩들을 서로 교배를 시켰더니 키가 큰 완두콩이 나오는 종자만을 얻을 수 있었다. 기존 발상으로는 키가 큰 것과 작은 것의 중간 키 정도가 되는 완두콩이 나와야 했는데 그렇지 않은 결과가 나온 것이다. 이런 식으로 한 가지 형질만이 겉으로 드러나는 것을 우열의 법칙이라고 하며, 이때 나타나게 되는 키가 큰 형질을 우성, 반대로 나타나지 않는 키가 작은 형질을 열성이라고 한다. 다음에는 이렇게 얻은 완두콩을 자가수분을 거쳐 다시 키워 보았다. 그러자 키가 큰 완두콩과 작은 완두콩의 비율이 3대 1로 나타났다. 이를 분리의 법칙이라고 한다. 또한 멘델은 완두콩의 키 이외에도 다른 형질로도 실험을 했다. 둥근 완두콩과 주름진 완두콩, 그리고 녹색 완두콩과 노란 완두콩에서도 같은 결과를 얻을 수 있었다. 더군다나 이러한 서로 다른 형질은 상관관계가 없이 서로 독립적으로 우열의 법칙과 분리의 법칙을 나타냈다. 이것을 독립의 법칙이라고 한다. 이 세 가지가 바로 멘델의 법칙이다.
멘델의 재발견
멘델의 법칙은 1884년 멘델이 사망한 후 16년 동안 빛을 보지 못하고 있다가 1900년에 와서 세 명의 연구자에 의해 다시 발견되었다. 네덜란드의 드 브리스는 1890년대에 달맞이꽃을 가지고 독자적인 실험을 해서 멘델의 법칙을 발견했으며 1895년에 멘델에 대해서 알게 되었다. 독일의 코렌스는 완두콩으로 실험을 해서 1899년에 멘델의 법칙을 다시 발견했으며 이때 멘델의 논문을 다시 읽어보았다고 한다. 그 후 멘델과 같은 실험을 했다는 사실에 논문 발표를 꺼리고 있다가 1900년에 드 브리스가 발표하기 직전의 논문에 멘델에 대한 언급이 없는 것을 보고 멘델을 소개하기 위해 "멘델의 법칙"이라는 논문을 썼다. 사실 드 브리스의 논문에는 멘델에 대한 언급이 있었지만 번역하는 도중에 빠졌다고 한다. 마지막으로 체르마크는 오스트리아에서 역시 완두콩을 가지고 연구하고 있었으며 드 브리스의 논문을 보고 급히 자신의 논문을 투고하여, 세 사람의 논문은 같이 게재되었다.
멘델 법칙의 한계와 발전
멘델의 법칙은 매우 훌륭한 이론이었으나 이후 연구가 계속되어 유전이 어떻게 이루어지는가를 더욱 잘 알게 된 이후에는 한정적인 상황에서만 성립한다는 사실이 알려지게 되었다. 우선 독립의 법칙은, 해당 형질을 나타내는 유전자들이 서로 다른 염색체에 있을 때에만 성립한다. 이것은 멘델이 매우 운이 좋았음을 알 수 있는 부분이기도 하다. 왜냐하면 완두콩의 상동염색체는 모두 7쌍({\displaystyle 2n=14}{\displaystyle 2n=14})이며, 멘델이 확인한 7개의
======================================================
유전자-JENE- DNA - The Genetic material for all forms of life on earth
DNA https://en.wikipedia.org/wiki/DNA
https://ko.wikipedia.org/wiki/%EC%9C%A0%EC%A0%84%EC%9E%90
===========================================================
유전자는 모든 생물의 고유한 특성에 대한 정보를 담고 있는 부분으로 다음 세대로 전해지는 물질로 DNA(디옥시리보핵산/Deoxyribo Nucleic Acid)서열 중에 특정 의미를 갖는 부분입니다.
위키백과, 우리 모두의 백과사전.
염색체(오른쪽 위)는 DNA가 실타래처럼 감겨 있는 구조로 되어 있다. 유전자는 DNA의 이중 나선 한 구간을 차지하
유전자란 - 수산·해양 LMO 안전성센터 - 국립수산과학원https://www.nifs.go.kr › lmo › lmo › lmo4_11
•
Feedback
유전자 - 나무위키https://namu.wiki › 유전자
·
Translate this page
Oct 12, 2022 — 자가 복제가 되는 성질의 분자 조합물이자 부모가 자식에게 특성을 물려주는 현상인 유전을 일으키는 단위이다. 건물을 짓기 위해 설계도가 필요하듯, ...
이기적 유전자 · 유전자 검사 · DNA
유전자 - 위키백과, 우리 모두의 백과사전https://ko.wikipedia.org › wiki › 유...
·
Translate this page
유전자(遺傳子, 영어: gene)는 유전의 기본단위이다. 지구상의 모든 생물은 유전자를 지니고 있다. 유전자에는 생물의 세포를 구성하고 유지하고, 이것들이 유기적인 ...
유전자 발현 · 유전자 이동 · 유전자형 · 위유전자
유전자와 염색체 - 기초 - MSD 매뉴얼 - 일반인용https://www.msdmanuals.com › 유전학
·
Translate this page
유전자형(또는 유전체)은 사람의 고유한 유전자 조합이나 유전자 구조를 의미합니다. 따라서 유전자형은 사람의 신체가 단백질을 합성하는 기제뿐 아니라 해당 신체가 구축 ...
유전자와 검사 | 유전학이란 | 의학유전학강좌 - 서울아산병원https://www.amc.seoul.kr › content
·
Translate this page
유전자는 DNA로 구성된 유전정보단위로서, 세포의 생명현상을 유지하고 특정한 기능을 수행하는데 필요한 모든 단백질을 만들기 위해 완벽한 명령체제를 지시 전달하는 ...
일반적 개요 · 암유전자검사는 현재 어느 단계... · 유전자검사의 위험요인은 무엇...
유전자(gene) | 알기쉬운의학용어 | 의료정보 - 서울아산병원https://amc.seoul.kr › easymediterm
·
Translate this page
유전자란 유전 형질을 나타내는 원인이 되는 인자입니다. 부모의 특징이 다음 세대인 자식에게 나타날 때, 그 특징을 만들어내는 인자로 유전 정보의 기본 단위를 말합니다 ...
유전자는 어떻게 우리 몸의 모양과 기능을 만들어낼까?https://www.sciencetimes.co.kr › news
·
Translate this page
Apr 9, 2021 — 유전자는 우리 몸을 이루는 세포의 핵 속에 있다. 세포핵에는 DNA가 있는데, 이 DNA에 유전자가 있다. DNA의 기본 단위는 염기와 당, 인산이 결합한 ...
유전자 - 위키낱말사전https://ko.wiktionary.org › wiki › 유...
·
Translate this page
1. 유전 형질을 지닌 단위, 염기서열 속에 들어있다. 번역. 그리스
======================================
The largest scientific study of its kind estimates that Earth could play host to more than 1 trillion different species, which means we've probably only identified a vanishingly small proportion of them – only about one-thousandth of 1 percent.
life forms -- 5.6 million species
A life form or lifeform is an entity that is living.[1][2]
Estimates on the number of Earth's current species range from 10 million to 14 million,[3] of which about 1.2 million have been documented and over 86 percent have not yet been described.[4] More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described.[5]
More than 99% of all species, amounting to over five billion species,[6] that ever lived on Earth are estimated to be extinct.[7][8]
Frohttps://en.wikipedia.org/wiki/Genem Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the heritable unit for transmission of biological traits. For other uses, see Gene (disambiguation).
Chromosome
(107 - 1010 bp)
DNA
Gene
(103 - 106 bp )
Function
A gene is a region of DNA that encodes function. A chromosome consists of a long strand of DNA containing many genes. A human chromosome can have up to 500 million base pairs of DNA with thousands of genes.
A gene is a sequence of DNA or RNA which codes for a molecule that has a function. The DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as gene–environment interactions. Some genetic traits are instantly visible, such as eye color or number of limbs, and some are not, such as blood type, risk for specific diseases, or the thousands of basic biochemical processes that comprise life.
Genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a protein, which cause different phenotypical traits. Usage of the term "having a gene" (e.g., "good genes," "hair colour gene") typically refers to containing a different allele of the same, shared gene. Genes evolve due to natural selection or survival of the fittest of the alleles.
The concept of a gene continues to be refined as new phenomena are discovered.[1] For example, regulatory regions of a gene can be far removed from its coding regions, and coding regions can be split into several exons. Some viruses store their genome in RNA instead of DNA and some gene products are functional non-coding RNAs. Therefore, a broad, modern working definition of a gene is any discrete locus of heritable, genomic sequence which affect an organism's traits by being expressed as a functional product or by regulation of gene expression.[2][3]
The term gene was introduced by Danish botanist, plant physiologist and geneticist Wilhelm Johannsen in 1905.[4] It is inspired by the ancient Greek: γόνος, gonos, that means offspring and procreation.
Contents [hide]
1
History
1.1
Discovery of discrete inherited units
1.2
Discovery of DNA
1.3
Modern synthesis and its successors
2
Molecular basis
2.1
DNA
2.2
Chromosomes
3
Structure and function
3.1
Structure
3.2
Functional definitions
4
Gene expression
4.1
Genetic code
4.2
Transcription
4.3
Translation
4.4
Regulation
4.5
RNA genes
5
Inheritance
5.1
Mendelian inheritance
5.2
DNA replication and cell division
5.3
Molecular inheritance
6
Molecular evolution
6.1
Mutation
6.2
Sequence homology
6.3
Origins of new genes
7
Genome
7.1
Number of genes
7.2
Essential genes
7.3
Genetic and genomic nomenclature
8
Genetic engineering
9
See also
10
References
10.1
Main textbook
10.2
References
10.3
Further reading
11
External links
History[edit]
Gregor Mendel
Main article: History of genetics
Discovery of discrete inherited units[edit]
The existence of discrete inheritable units was first suggested by Gregor Mendel (1822–1884).[5] From 1857 to 1864, in Brno (Czech Republic), he studied inheritance patterns in 8000 common edible pea plants, tracking distinct traits from parent to offspring. He described these mathematically as 2n combinations where n is the number of differing characteristics in the original peas. Although he did not use the term gene, he explained his results in terms of discrete inherited units that give rise to observable physical characteristics. This description prefigured Wilhelm Johannsen's distinction between genotype (the genetic material of an organism) and phenotype (the visible traits of that organism). Mendel was also the first to demonstrate independent assortment, the distinction between dominant and recessive traits, the distinction between a heterozygote and homozygote, and the phenomenon of discontinuous inheritance.
Prior to Mendel's work, the dominant theory of heredity was one of blending inheritance, which suggested that each parent contributed fluids to the fertilisation process and that the traits of the parents blended and mixed to produce the offspring. Charles Darwin developed a theory of inheritance he termed pangenesis, from Greek pan ("all, whole") and genesis ("birth") / genos ("origin").[6][7] Darwin used the term gemmule to describe hypothetical particles that would mix during reproduction.
Mendel's work went largely unnoticed after its first publication in 1866, but was rediscovered in the late 19th century by Hugo de Vries, Carl Correns, and Erich von Tschermak, who (claimed to have) reached similar conclusions in their own research.[8] Specifically, in 1889, Hugo de Vries published his book Intracellular Pangenesis,[9] in which he postulated that different characters have individual hereditary carriers and that inheritance of specific traits in organisms comes in particles. De Vries called these units "pangenes" (Pangens in German), after Darwin's 1868 pangenesis theory.
Sixteen years later, in 1905, Wilhelm Johannsen introduced the term 'gene'[4] and William Bateson that of 'genetics'[10] while Eduard Strasburger, amongst others, still used the term 'pangene' for the fundamental physical and functional unit of heredity.[11]
Discovery of DNA[edit]
Advances in understanding genes and inheritance continued throughout the 20th century. Deoxyribonucleic acid (DNA) was shown to be the molecular repository of genetic information by experiments in the 1940s to 1950s.[12][13] The structure of DNA was studied by Rosalind Franklin and Maurice Wilkins using X-ray crystallography, which led James D. Watson and Francis Crick to publish a model of the double-stranded DNA molecule whose paired nucleotide bases indicated a compelling hypothesis for the mechanism of genetic replication.[14][15]
In the early 1950s the prevailing view was that the genes in a chromosome acted like discrete entities, indivisible by recombination and arranged like beads on a string. The experiments of Benzer using mutants defective in the rII region of bacteriophage T4 (1955-1959) showed that individual genes have a simple linear structure and are likely to be equivalent to a linear section of DNA.[16][17]
Collectively, this body of research established the central dogma of molecular biology, which states that proteins are translated from RNA, which is transcribed from DNA. This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses. The modern study of genetics at the level of DNA is known as molecular genetics.
In 1972, Walter Fiers and his team at the University of Ghent were the first to determine the sequence of a gene: the gene for Bacteriophage MS2 coat protein.[18] The subsequent development of chain-termination DNA sequencing in 1977 by Frederick Sanger improved the efficiency of sequencing and turned it into a routine laboratory tool.[19] An automated version of the Sanger method was used in early phases of the Human Genome Project.[20]
Modern synthesis and its successors[edit]
Main article: Modern synthesis (20th century)
The theories developed in the early 20th century to integrate Mendelian genetics with Darwinian evolution are called the modern synthesis, a term introduced by Julian Huxley.[21]
Evolutionary biologists have subsequently modified this concept, such as George C. Williams' gene-centric view of evolution. He proposed an evolutionary concept of the gene as a unit of natural selection with the definition: "that which segregates and recombines with appreciable frequency."[22]:24 In this view, the molecular gene transcribes as a unit, and the evolutionary gene inherits as a unit. Related ideas emphasizing the centrality of genes in evolution were popularized by Richard Dawkins.[23][24]
Molecular basis[edit]
Main article: DNA
The chemical structure of a four base pair fragment of a DNA double helix. The sugar-phosphate backbone chains run in opposite directions with the bases pointing inwards, base-pairing A to T and C to G with hydrogen bonds.
DNA[edit]
The vast majority of living organisms encode their genes in long strands of DNA (deoxyribonucleic acid). DNA consists of a chain made from four types of nucleotide subunits, each composed of: a five-carbon sugar (2'-deoxyribose), a phosphate group, and one of the four bases adenine, cytosine, guanine, and thymine.[25]:2.1
Two chains of DNA twist around each other to form a DNA double helix with the phosphate-sugar backbone spiralling around the outside, and the bases pointing inwards with adenine base pairing to thymine and guanine to cytosine. The specificity of base pairing occurs because adenine and thymine align to form two hydrogen bonds, whereas cytosine and guanine form three hydrogen bonds. The two strands in a double helix must therefore be complementary, with their sequence of bases matching such that the adenines of one strand are paired with the thymines of the other strand, and so on.[25]:4.1
Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose; this is known as the 3' end of the molecule. The other end contains an exposed phosphate group; this is the 5' end. The two strands of a double-helix run in opposite directions. Nucleic acid synthesis, including DNA replication and transcription occurs in the 5'→3' direction, because new nucleotides are added via a dehydration reaction that uses the exposed 3' hydroxyl as a nucleophile.[26]:27.2
The expression of genes encoded in DNA begins by transcribing the gene into RNA, a second type of nucleic acid that is very similar to DNA, but whose monomers contain the sugar ribose rather than deoxyribose. RNA also contains the base uracil in place of thymine. RNA molecules are less stable than DNA and are typically single-stranded. Genes that encode proteins are composed of a series of three-nucleotide sequences called codons, which serve as the "words" in the genetic "language". The genetic code specifies the correspondence during protein translation between codons and amino acids. The genetic code is nearly the same for all known organisms.[25]:4.1
Chromosomes[edit]
Fluorescent microscopy image of a human female karyotype, showing 23 pairs of chromosomes . The DNA is stained red, with regions rich in housekeeping genes further stained in green. The largest chromosomes are around 10 times the size of the smallest.[27]
The total complement of genes in an organism or cell is known as its genome, which may be stored on one or more chromosomes. A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded.[25]:4.2 The region of the chromosome at which a particular gene is located is called its locus. Each locus contains one allele of a gene; however, members of a population may have different alleles at the locus, each with a slightly different gene sequence.
The majority of eukaryotic genes are stored on a set of large, linear chromosomes. The chromosomes are packed within the nucleus in complex with storage proteins called histones to form a unit called a nucleosome. DNA packaged and condensed in this way is called chromatin.[25]:4.2 The manner in which DNA is stored on the histones, as well as chemical modifications of the histone itself, regulate whether a particular region of DNA is accessible for gene expression. In addition to genes, eukaryotic chromosomes contain sequences involved in ensuring that the DNA is copied without degradation of end regions and sorted into daughter cells during cell division: replication origins, telomeres and the centromere.[25]:4.2 Replication origins are the sequence regions where DNA replication is initiated to make two copies of the chromosome. Telomeres are long stretches of repetitive sequence that cap the ends of the linear chromosomes and prevent degradation of coding and regulatory regions during DNA replication. The length of the telomeres decreases each time the genome is replicated and has been implicated in the aging process.[28] The centromere is required for binding spindle fibres to separate sister chromatids into daughter cells during cell division.[25]:18.2
Prokaryotes (bacteria and archaea) typically store their genomes on a single large, circular chromosome. Similarly, some eukaryotic organelles contain a remnant circular chromosome with a small number of genes.[25]:14.4 Prokaryotes sometimes supplement their chromosome with additional small circles of DNA called plasmids, which usually encode only a few genes and are transferable between individuals. For example, the genes for antibiotic resistance are usually encoded on bacterial plasmids and can be passed between individual cells, even those of different species, via horizontal gene transfer.[29]
Whereas the chromosomes of prokaryotes are relatively gene-dense, those of eukaryotes often contain regions of DNA that serve no obvious function. Simple single-celled eukaryotes have relatively small amounts of such DNA, whereas the genomes of complex multicellular organisms, including humans, contain an absolute majority of DNA without an identified function.[30] This DNA has often been referred to as "junk DNA". However, more recent analyses suggest that, although protein-coding DNA makes up barely 2% of the human genome, about 80% of the bases in the genome may be expressed, so the term "junk DNA" may be a misnomer.[3]
Structure and function[edit]
Structure[edit]
Regulatory sequence
Regulatory sequence
Enhancer
/silencer
Promoter
5'UTR
Open reading frame
3'UTR
Enhancer
/silencer
Proximal
Core
Start
Stop
Terminator
Transcription
DNA
Exon
Exon
Exon
Intron
Intron
Post-transcriptional
modification
Pre-
mRNA
Protein coding region
5'cap
Poly-A tail
Translation
Mature
mRNA
Protein
The structure of a eukaryotic protein-coding gene. Regulatory sequence controls when and where expression occurs for the protein coding region (red). Promoter and enhancer regions (yellow) regulate the transcription of the gene into a pre-mRNA which is modified to remove introns (light grey) and add a 5' cap and poly-A tail (dark grey). The mRNA 5' and 3' untranslated regions (blue) regulate translation into the final protein product.[31]
Polycistronic operon
Regulatory sequence
Regulatory sequence
Enhancer
Enhancer
/silencer
/silencer
Operator
Promoter
5'UTR
ORF
ORF
UTR
3'UTR
Start
Start
Stop
Stop
Terminator
Transcription
DNA
RBS
RBS
Protein coding region
Protein coding region
mRNA
Translation
Protein
The structure of a prokaryotic operon of protein-coding genes. Regulatory sequence controls when expression occurs for the multiple protein coding regions (red). Promoter, operator and enhancer regions (yellow) regulate the transcription of the gene into an mRNA. The mRNA untranslated regions (blue) regulate translation into the final protein products.[31]
The structure of a gene consists of many elements of which the actual protein coding sequence is often only a small part. These include DNA regions that are not transcribed as well as untranslated regions of the RNA.
Flanking the open reading frame, genes contain a regulatory sequence that is required for their expression. First, genes require a promoter sequence. The promoter is recognized and bound by transcription factors and RNA polymerase to initiate transcription.[25]:7.1 The recognition typically occurs as a consensus sequence like the TATA box. A gene can have more than one promoter, resulting in messenger RNAs (mRNA) that differ in how far they extend in the 5' end.[32] Highly transcribed genes have "strong" promoter sequences that form strong associations with transcription factors, thereby initiating transcription at a high rate. Others genes have "weak" promoters that form weak associations with transcription factors and initiate transcription less frequently.[25]:7.2 Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters.[25]:7.3
Additionally, genes can have regulatory regions many kilobases upstream or downstream of the open reading frame that alter expression. These act by binding to transcription factors which then cause the DNA to loop so that the regulatory sequence (and bound transcription factor) become close to the RNA polymerase binding site.[33] For example, enhancers increase transcription by binding an activator protein which then helps to recruit the RNA polymerase to the promoter; conversely silencers bind repressor proteins and make the DNA less available for RNA polymerase.[34]
The transcribed pre-mRNA contains untranslated regions at both ends which contain a ribosome binding site, terminator and start and stop codons.[35] In addition, most eukaryotic open reading frames contain untranslated introns which are removed before the exons are translated. The sequences at the ends of the introns, dictate the splice sites to generate the final mature mRNA which encodes the protein or RNA product.[36]
Many prokaryotic genes are organized into operons, with multiple protein-coding sequences that are transcribed as a unit.[37][38] The genes in an operon are transcribed as a continuous messenger RNA, referred to as a polycistronic mRNA. The term cistron in this context is equivalent to gene. The transcription of an operon’s mRNA is often controlled by a repressor that can occur in an active or inactive state depending on the presence of certain specific metabolites.[39] When active, the repressor binds to a DNA sequence at the beginning of the operon, called the operator region, and represses transcription of the operon; when the repressor is inactive transcription of the operon can occur (see e.g. Lac operon). The products of operon genes typically have related functions and are involved in the same regulatory network.[25]:7.3
Functional definitions[edit]
Defining exactly what section of a DNA sequence comprises a gene is difficult.[1] Regulatory regions of a gene such as enhancers do not necessarily have to be close to the coding sequence on the linear molecule because the intervening DNA can be looped out to bring the gene and its regulatory region into proximity. Similarly, a gene's introns can be much larger than its exons. Regulatory regions can even be on entirely different chromosomes and operate in trans to allow regulatory regions on one chromosome to come in contact with target genes on another chromosome.[40][41]
Early work in molecular genetics suggested the concept that one gene makes one protein. This concept (originally called the one gene-one enzyme hypothesis) emerged from an influential 1941 paper by George Beadle and Edward Tatum on experiments with mutants of the fungus Neurospora crassa.[42] Norman Horowitz, an early colleague on the Neurospora research, reminisced in 2004 that “these experiments founded the science of what Beadle and Tatum called biochemical genetics. In actuality they proved to be the opening gun in what became molecular genetics and all the developments that have followed from that.”[43] The one gene-one protein concept has been refined since the discovery of genes that can encode multiple proteins by alternative splicing and coding sequences split in short section across the genome whose mRNAs are concatenated by trans-splicing.[3][44][45]
A broad operational definition is sometimes used to encompass the complexity of these diverse phenomena, where a gene is defined as a union of genomic sequences encoding a coherent set of potentially overlapping functional products.[10] This definition categorizes genes by their functional products (proteins or RNA) rather than their specific DNA loci, with regulatory elements classified as gene-associated regions.[10]
Gene expression[edit]
Main article: Gene expression
In all organisms, two steps are required to read the information encoded in a gene's DNA and produce the protein it specifies. First, the gene's DNA is transcribed to messenger RNA (mRNA).[25]:6.1 Second, that mRNA is translated to protein.[25]:6.2 RNA-coding genes must still go through the first step, but are not translated into protein.[46] The process of producing a biologically functional molecule of either RNA or protein is called gene expression, and the resulting molecule is called a gene product.
Genetic code[edit]
Schematic of a single-stranded RNA molecule illustrating a series of three-base codons. Each three-nucleotide codon corresponds to an amino acid when translated to protein
The nucleotide sequence of a gene's DNA specifies the amino acid sequence of a protein through the genetic code. Sets of three nucleotides, known as codons, each correspond to a specific amino acid.[25]:6 The principle that three sequential bases of DNA code for each amino acid was demonstrated in 1961 using frameshift mutations in the rIIB gene of bacteriophage T4[47] (see Crick, Brenner et al. experiment).
Additionally, a "start codon", and three "stop codons" indicate the beginning and end of the protein coding region. There are 64 possible codons (four possible nucleotides at each of three positions, hence 43 possible codons) and only 20 standard amino acids; hence the code is redundant and multiple codons can specify the same amino acid. The correspondence between codons and amino acids is nearly universal among all known living organisms.[48]
Transcription[edit]
Transcription produces a single-stranded RNA molecule known as messenger RNA, whose nucleotide sequence is complementary to the DNA from which it was transcribed.[25]:6.1 The mRNA acts as an intermediate between the DNA gene and its final protein product. The gene's DNA is used as a template to generate a complementary mRNA. The mRNA matches the sequence of the gene's DNA coding strand because it is synthesised as the complement of the template strand. Transcription is performed by an enzyme called an RNA polymerase, which reads the template strand in the 3' to 5' direction and synthesizes the RNA from 5' to 3'. To initiate transcription, the polymerase first recognizes and binds a promoter region of the gene. Thus, a major mechanism of gene regulation is the blocking or sequestering the promoter region, either by tight binding by repressor molecules that physically block the polymerase, or by organizing the DNA so that the promoter region is not accessible.[25]:7
In prokaryotes, transcription occurs in the cytoplasm; for very long transcripts, translation may begin at the 5' end of the RNA while the 3' end is still being transcribed. In eukaryotes, transcription occurs in the nucleus, where the cell's DNA is stored. The RNA molecule produced by the polymerase is known as the primary transcript and undergoes post-transcriptional modifications before being exported to the cytoplasm for translation. One of the modifications performed is the splicing of introns which are sequences in the transcribed region that do not encode protein. Alternative splicing mechanisms can result in mature transcripts from the same gene having different sequences and thus coding for different proteins. This is a major form of regulation in eukaryotic cells and also occurs in some prokaryotes.[25]:7.5[49]
Translation[edit]
Protein coding genes are transcribed to an mRNA intermediate, then translated to a functional protein. RNA-coding genes are transcribed to a functional non-coding RNA. (PDB: 3BSE, 1OBB, 3TRA)
Translation is the process by which a mature mRNA molecule is used as a template for synthesizing a new protein.[25]:6.2 Translation is carried out by ribosomes, large complexes of RNA and protein responsible for carrying out the chemical reactions to add new amino acids to a growing polypeptide chain by the formation of peptide bonds. The genetic code is read three nucleotides at a time, in units called codons, via interactions with specialized RNA molecules called transfer RNA (tRNA). Each tRNA has three unpaired bases known as the anticodon that are complementary to the codon it reads on the mRNA. The tRNA is also covalently attached to the amino acid specified by the complementary codon. When the tRNA binds to its complementary codon in an mRNA strand, the ribosome attaches its amino acid cargo to the new polypeptide chain, which is synthesized from amino terminus to carboxyl terminus. During and after synthesis, most new proteins must fold to their active three-dimensional structure before they can carry out their cellular functions.[25]:3
Regulation[edit]
Genes are regulated so that they are expressed only when the product is needed, since expression draws on limited resources.[25]:7 A cell regulates its gene expression depending on its external environment (e.g. available nutrients, temperature and other stresses), its internal environment (e.g. cell division cycle, metabolism, infection status), and its specific role if in a multicellular organism. Gene expression can be regulated at any step: from transcriptional initiation, to RNA processing, to post-translational modification of the protein. The regulation of lactose metabolism genes in E. coli (lac operon) was the first such mechanism to be described in 1961.[50]
RNA genes[edit]
A typical protein-coding gene is first copied into RNA as an intermediate in the manufacture of the final protein product.[25]:6.1 In other cases, the RNA molecules are the actual functional products, as in the synthesis of ribosomal RNA and transfer RNA. Some RNAs known as ribozymes are capable of enzymatic function, and microRNA has a regulatory role. The DNA sequences from which such RNAs are transcribed are known as non-coding RNA genes.[46]
Some viruses store their entire genomes in the form of RNA, and contain no DNA at all.[51][52] Because they use RNA to store genes, their cellular hosts may synthesize their proteins as soon as they are infected and without the delay in waiting for transcription.[53] On the other hand, RNA retroviruses, such as HIV, require the reverse transcription of their genome from RNA into DNA before their proteins can be synthesized. RNA-mediated epigenetic inheritance has also been observed in plants and very rarely in animals.[54]
Inheritance[edit]
Inheritance of a gene that has two different alleles (blue and white). The gene is located on an autosomal chromosome. The white allele is recessive to the blue allele. The probability of each outcome in the children's generation is one quarter, or 25 percent.
Main articles: Mendelian inheritance and Heredity
Organisms inherit their genes from their parents. Asexual organisms simply inherit a complete copy of their parent's genome. Sexual organisms have two copies of each chromosome because they inherit one complete set from each parent.[25]:1
Mendelian inheritance[edit]
According to Mendelian inheritance, variations in an organism's phenotype (observable physical and behavioral characteristics) are due in part to variations in its genotype (particular set of genes). Each gene specifies a particular trait with different sequence of a gene (alleles) giving rise to different phenotypes. Most eukaryotic organisms (such as the pea plants Mendel worked on) have two alleles for each trait, one inherited from each parent.[25]:20
Alleles at a locus may be dominant or recessive; dominant alleles give rise to their corresponding phenotypes when paired with any other allele for the same trait, whereas recessive alleles give rise to their corresponding phenotype only when paired with another copy of the same allele. If you know the genotypes of the organisms, you can determine which alleles are dominant and which are recessive. For example, if the allele specifying tall stems in pea plants is dominant over the allele specifying short stems, then pea plants that inherit one tall allele from one parent and one short allele from the other parent will also have tall stems. Mendel's work demonstrated that alleles assort independently in the production of gametes, or germ cells, ensuring variation in the next generation. Although Mendelian inheritance remains a good model for many traits determined by single genes (including a number of well-known genetic disorders) it does not include the physical processes of DNA replication and cell division.[55][56]
DNA replication and cell division[edit]
The growth, development, and reproduction of organisms relies on cell division; the process by which a single cell divides into two usually identical daughter cells. This requires first making a duplicate copy of every gene in the genome in a process called DNA replication.[25]:5.2 The copies are made by specialized enzymes known as DNA polymerases, which "read" one strand of the double-helical DNA, known as the template strand, and synthesize a new complementary strand. Because the DNA double helix is held together by base pairing, the sequence of one strand completely specifies the sequence of its complement; hence only one strand needs to be read by the enzyme to produce a faithful copy. The process of DNA replication is semiconservative; that is, the copy of the genome inherited by each daughter cell contains one original and one newly synthesized strand of DNA.[25]:5.2
The rate of DNA replication in living cells was first measured as the rate of phage T4 DNA elongation in phage-infected E. coli and found to be impressively rapid.[57] During the period of exponential DNA increase at 37 °C, the rate of elongation was 749 nucleotides per second.
After DNA replication is complete, the cell must physically separate the two copies of the genome and divide into two distinct membrane-bound cells.[25]:18.2 In prokaryotes (bacteria and archaea) this usually occurs via a relatively simple process called binary fission, in which each circular genome attaches to the cell membrane and is separated into the daughter cells as the membrane invaginates to split the cytoplasm into two membrane-bound portions. Binary fission is extremely fast compared to the rates of cell division in eukaryotes. Eukaryotic cell division is a more complex process known as the cell cycle; DNA replication occurs during a phase of this cycle known as S phase, whereas the process of segregating chromosomes and splitting the cytoplasm occurs during M phase.[25]:18.1
Molecular inheritance[edit]
The duplication and transmission of genetic material from one generation of cells to the next is the basis for molecular inheritance, and the link between the classical and molecular pictures of genes. Organisms inherit the characteristics of their parents because the cells of the offspring contain copies of the genes in their parents' cells. In asexually reproducing organisms, the offspring will be a genetic copy or clone of the parent organism. In sexually reproducing organisms, a specialized form of cell division called meiosis produces cells called gametes or germ cells that are haploid, or contain only one copy of each gene.[25]:20.2 The gametes produced by females are called eggs or ova, and those produced by males are called sperm. Two gametes fuse to form a diploid fertilized egg, a single cell that has two sets of genes, with one copy of each gene from the mother and one from the father.[25]:20
During the process of meiotic cell division, an event called genetic recombination or crossing-over can sometimes occur, in which a length of DNA on one chromatid is swapped with a length of DNA on the corresponding homologous non-sister chromatid. This can result in reassortment of otherwise linked alleles.[25]:5.5 The Mendelian principle of independent assortment asserts that each of a parent's two genes for each trait will sort independently into gametes; which allele an organism inherits for one trait is unrelated to which allele it inherits for another trait. This is in fact only true for genes that do not reside on the same chromosome, or are located very far from one another on the same chromosome. The closer two genes lie on the same chromosome, the more closely they will be associated in gametes and the more often they will appear together; genes that are very close are essentially never separated because it is extremely unlikely that a crossover point will occur between them. This is known as genetic linkage.[58]
Molecular evolution[edit]
Main article: Molecular evolution
Mutation[edit]
DNA replication is for the most part extremely accurate, however errors (mutations) do occur.[25]:7.6 The error rate in eukaryotic cells can be as low as 10−8 per nucleotide per replication,[59][60] whereas for some RNA viruses it can be as high as 10−3.[61] This means that each generation, each human genome accumulates 1–2 new mutations.[61] Small mutations can be caused by DNA replication and the aftermath of DNA damage and include point mutations in which a single base is altered and frameshift mutations in which a single base is inserted or deleted. Either of these mutations can change the gene by missense (change a codon to encode a different amino acid) or nonsense (a premature stop codon).[62] Larger mutations can be caused by errors in recombination to cause chromosomal abnormalities including the duplication, deletion, rearrangement or inversion of large sections of a chromosome. Additionally, DNA repair mechanisms can introduce mutational errors when repairing physical damage to the molecule. The repair, even with mutation, is more important to survival than restoring an exact copy, for example when repairing double-strand breaks.[25]:5.4
When multiple different alleles for a gene are present in a species's population it is called polymorphic. Most different alleles are functionally equivalent, however some alleles can give rise to different phenotypic traits. A gene's most common allele is called the wild type, and rare alleles are called mutants. The genetic variation in relative frequencies of different alleles in a population is due to both natural selection and genetic drift.[63] The wild-type allele is not necessarily the ancestor of less common alleles, nor is it necessarily fitter.
Most mutations within genes are neutral, having no effect on the organism's phenotype (silent mutations). Some mutations do not change the amino acid sequence because multiple codons encode the same amino acid (synonymous mutations). Other mutations can be neutral if they lead to amino acid sequence changes, but the protein still functions similarly with the new amino acid (e.g. conservative mutations). Many mutations, however, are deleterious or even lethal, and are removed from populations by natural selection. Genetic disorders are the result of deleterious mutations and can be due to spontaneous mutation in the affected individual, or can be inherited. Finally, a small fraction of mutations are beneficial, improving the organism's fitness and are extremely important for evolution, since their directional selection leads to adaptive evolution.[25]:7.6
Sequence homology[edit]
A sequence alignment, produced by ClustalO, of mammalian histone proteins
Genes with a most recent common ancestor, and thus a shared evolutionary ancestry, are known as homologs.[64] These genes appear either from gene duplication within an organism's genome, where they are known as paralogous genes, or are the result of divergence of the genes after a speciation event, where they are known as orthologous genes,[25]:7.6 and often perform the same or similar functions in related organisms. It is often assumed that the functions of orthologous genes are more similar than those of paralogous genes, although the difference is minimal.[65][66]
The relationship between genes can be measured by comparing the sequence alignment of their DNA.[25]:7.6 The degree of sequence similarity between homologous genes is called conserved sequence. Most changes to a gene's sequence do not affect its function and so genes accumulate mutations over time by neutral molecular evolution. Additionally, any selection on a gene will cause its sequence to diverge at a different rate. Genes under stabilizing selection are constrained and so change more slowly whereas genes under directional selection change sequence more rapidly.[67] The sequence differences between genes can be used for phylogenetic analyses to study how those genes have evolved and how the organisms they come from are related.[68][69]
Origins of new genes[edit]
Evolutionary fate of duplicate genes.
The most common source of new genes in eukaryotic lineages is gene duplication, which creates copy number variation of an existing gene in the genome.[70][71] The resulting genes (paralogs) may then diverge in sequence and in function. Sets of genes formed in this way comprise a gene family. Gene duplications and losses within a family are common and represent a major source of evolutionary biodiversity.[72] Sometimes, gene duplication may result in a nonfunctional copy of a gene, or a functional copy may be subject to mutations that result in loss of function; such nonfunctional genes are called pseudogenes.[25]:7.6
"Orphan" genes, whose sequence shows no similarity to existing genes, are less common than gene duplicates. Estimates of the number of genes with no homologs outside humans range from 18[73] to 60.[74] Two primary sources of orphan protein-coding genes are gene duplication followed by extremely rapid sequence change, such that the original relationship is undetectable by sequence comparisons, and de novo conversion of a previously non-coding sequence into a protein-coding gene.[75] De novo genes are typically shorter and simpler in structure than most eukaryotic genes, with few if any introns.[70] Over long evolutionary time periods, de novo gene birth may be responsible for a significant fraction of taxonomically-restricted gene families.[76]
Horizontal gene transfer refers to the transfer of genetic material through a mechanism other than reproduction. This mechanism is a common source of new genes in prokaryotes, sometimes thought to contribute more to genetic variation than gene duplication.[77] It is a common means of spreading antibiotic resistance, virulence, and adaptive metabolic functions.[29][78] Although horizontal gene transfer is rare in eukaryotes, likely examples have been identified of protist and alga genomes containing genes of bacterial origin.[79][80]
Genome[edit]
The genome is the tot
====
인체를 구성하는 세포들은 크기도 제각각이다. 가장 작은 적혈구(지름 7~8μm)와 가장 큰 골격근 세포(지름 100μm, 길이 2~3cm) 차이는 100만배가 넘어, 땃쥐와 대왕고래의 몸집 차이와 비슷하다.Sep 26, 2023
작을수록 많고 크면 적다…인체 세포도 '크기와 수 반비례법칙'
====
Cell Size - 4.2: 세포 크기
세포의 크기는 유기체 마다, 또 같은 유기체 사이에서도 매우 다양합니다. 예를 들어 가장 작은 박테리아는 직경이 0.1마이크로미터(μm)이며, 대부분의 진핵 ...
[장수철의 생물학을 위하여] 세포의 크기
서울신문
Dec 11, 2018 — 세포는 지름이 0.01~0.1㎜ 정도이다. 결국 코끼리, 버섯, 거미가 크기가 다른 것은 세포의 수가 다르기 때문이다. 코끼리는 세포 수가 거미보다 많다는 말이다.
[기초]세포의 모양과 크기
Jun 20, 2005 — 하지만 대부분의 진핵 세포는 직경이 10μm -1백μm 사이다. (1) 진화는 세포의 크기를 작게 유지하면서 개체 크기의 증가를 조절하기 위해 세포의 수를 ...
====
Cell biology is the study of cell structure and function, and it revolves around the concept that the cell is the fundamental unit of life.
Cell Biology | Learn Science at Scitable - Nature
https://www.google.ca/search?q=cell+biology&sxsrf=AB5stBidukaXPR_702kfNc_zLbruKeTqew%3A1690711776831&source=hp&ei=4DbGZOKvMM-80PEPw6K38As&iflsig=AD69kcEAAAAAZMZE8EyFDt5bgGJWUacnhDX6p-TC54gp&oq=&gs_lp=Egdnd3Mtd2l6IgAqAggAMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnSJcNUABYAHABeACQAQCYAQCgAQCqAQC4AQHIAQCoAgo&sclient=gws-wiz
=======================
세포 생화학 반응
세포 안에서 일어나는 모든 생화학 반응을 일컬어 대사작용(metabolism)이라 한다. 세. 포는 대사작용을 통해 에너지와 환원력을 만들고 세포를 구성하는 고분자 물질 ...
=====================================-
(metabolism)
https://www.google.ca/search?q=metabolism&sxsrf=AB5stBiX-RaICXS8wj0BrJ38ul3R10X3lQ%3A1690712119801&source=hp&ei=NzjGZPuWLq_G0PEP__OXmA0&iflsig=AD69kcEAAAAAZMZGRzC_kiPYLT8Yxr1OWsU83szU0Xmb&oq=&gs_lp=Egdnd3Mtd2l6IgAqAggFMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnSL4jUABYAHABeACQAQCYAQCgAQCqAQC4AQHIAQCoAgo&sclient=gws-wiz
세포 생화학 반응
https://www.google.ca/search?q=%EC%83%9D%ED%99%94%ED%95%99%EB%B0%98%EC%9D%91&sxsrf=AB5stBhCuKcj8WnoQbFnJ44-5mVlosaXjg%3A1690711914023&source=hp&ei=aTfGZK2APPWt0PEPpO6msAo&iflsig=AD69kcEAAAAAZMZFek3YmJWOMZdNl2iztcUftjldZwjc&oq=&gs_lp=Egdnd3Mtd2l6IgAqAggBMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnMgcQIxjqAhgnSJkOUABYAHABeACQAQCYAQCgAQCqAQC4AQHIAQCoAgo&sclient=gws-wiz
==============
체세포분열(mitosis /maɪˈtoʊsɪs/; 유사분열)은 복제된 염색체가 두 개의 세포핵으로 분리되는 세포 주기의 한 부분이다. 세포 분열은 전체 염색체 수 ..
감수분열 - 위키백과, 우리 모두의 백과사전https://ko.wikipedia.org › wiki › 감...
감수분열(meiosis, Listen/maɪˈoʊsɪs/, 감소하는 분열이라는 점에서 그리스어로 줄어든다는 의미의 μείωσις, meiosis에서 유래함)이란 유성 생식을 하는 생물들이 정자 ...
https://ko.wikipedia.org/wiki/%EA%B0%90%EC%88%98%EB%B6%84%EC%97%B4
세포생물학에서 체세포분열(mitosis /maɪˈtoʊsɪs/; 유사분열)은 복제된 염색체가 두 개의 세포핵으로 분리되는 세포 주기의 한 부분이다. 세포 분열은 전체 염색체 수
https://ko.wikipedia.org/wiki/%EC%B2%B4%EC%84%B8%ED%8F%AC%EB%B6%84%EC%97%B4
======================================================================================...
cell theory
https://www.google.ca/search?q=cell+theory&tbm=isch&ved=2ahUKEwiu-qDyy7r8AhU6ADQIHUKACLUQ2-cCegQIABAA&oq=cell+&gs_lcp=CgNpbWcQARgJMgQIIxAnMgQIIxAnMgQIABBDMggIABCABBCxAzIICAAQgAQQsQMyCAgAEIAEELEDMggIABCABBCxAzIICAAQgAQQsQMyBQgAEIAEMgUIABCABFDODFjODGDLN2gAcAB4AIABpwWIAcMIkgEFNC0xLjGYAQCgAQGqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=fxa8Y-6-E7qA0PEPwoCiqAs
===============================================
cellhttps://www.google.ca/search?q=cell&dcr=0&sxsrf=ALeKk00-4ESN8NLPcmJvBgcC4zVvxHU00g:1610793365549&tbm=isch&source=iu&ictx=1&fir=jdQpUZ4xClUx4M%252CdHCEwQt_r3xVsM%252C_&vet=1&usg=AI4_-kQzXtRTAxxlgHz_fm3qoP1YTKqBAw&sa=X&ved=2ahUKEwjhj_DyoKDuAhUICTQIHcZNBkoQ_h16BAgMEAE#imgrc=jdQpUZ4xClUx4M
세포
생물의 구조적, 기능적 단위
세포는 모든 생물체의 구조적, 기능적 기본 단위이다. 세포에 대해 연구하는 학문을 세포생물학이라고 한다. 세포는 세포막으로 둘러싸인 세포질로 구성되어 있으며, 단백질 및 핵산과 같은 많은 생체분자들을 포함하고 있다. 생물은 단세포 생물 또는 다세포 생물로 분류할 수 있다. 식물 및 동물의 세포수는 생물종마다 다르며, 사람은 약 60조 개의 세포를 가지고 있…
Cell (biology) - Wikipedia
https://en.wikipedia.org/wiki/Cell_(biology)
The cell is the basic structural and functional unit of life forms. Every cell consists of a cytoplasm enclosed within a membrane, and contains many biomolecules such as proteins, DNA and RNA, as well as many small molecules of nutrients and metabolites. The term comes from the Latin word cellula meaning … 더 보기
Cell types
Cells are of two types: eukaryotic, which contain a nucleus, and prokaryotic cells, which do not have a nucleus, but a nucleoid region is still present. Prokaryotes are single-celled organisms, while eukaryotes may … 더 보기
Cellular processes 이미지
Origins 이미지
Subcellular components
All cells, whether prokaryotic or eukaryotic, have a membrane that envelops the cell, regulates what moves in and out (selectively … 더 보기
Cellular processes
Replication
Cell division involves a single cell (called a mother cell) dividing into two daughter cells. This leads to growth in multicellular organisms (the … 더 보기
Multicellularity
Cell specialization/differentiation
Multicellular organisms are organisms that consist of more than one cell, in contrast to single-celled organisms.
In complex … 더 보기
Cell shape, also called cell morphology, has been hypothesized to form from the arrangement and movement of the cytoskeleton. Many advancements in the study of cell morphology come from studying simple bacteria such as Staphylococcus aureus 더 보기
Structures outside the cell membrane
Many cells also have structures which exist wholly or partially outside the cell membrane. These structures are notable because they are not protected from the external environment by the semipermeable cell membrane. In order to assemble these … 더 보기
Origins
The origin of cells has to do with the origin of life, which began the history of life on Earth.
Origin of the first cell 더 보기
CC-BY-SA 라이선스가 적용되는 Wikipedia 텍스트
원본: Wikipedia
=======================================
cell
https://www.google.ca/search?q=cell&dcr=0&sxsrf=ALeKk00-4ESN8NLPcmJvBgcC4zVvxHU00g:1610793365549&tbm=isch&source=iu&ictx=1&fir=jdQpUZ4xClUx4M%252CdHCEwQt_r3xVsM%252C_&vet=1&usg=AI4_-kQzXtRTAxxlgHz_fm3qoP1YTKqBAw&sa=X&ved=2ahUKEwjhj_DyoKDuAhUICTQIHcZNBkoQ_h16BAgMEAE
==================================
cell division
https://www.google.ca/search?q=cell+division&tbm=isch&ved=2ahUKEwiE58zRyrr8AhUOBDQIHZcrCLQQ2-cCegQIABAA&oq=cell&gs_lcp=CgNpbWcQARgJMgQIIxAnMgQIABBDMgcIABCxAxBDMgcIABCxAxBDMgcIABCxAxBDMggIABCABBCxAzIECAAQQzIHCAAQsQMQQzIFCAAQgAQyBwgAELEDEENQAFgAYNaIAmgAcAB4AIABhgKIAbwDkgEFMC4xLjGYAQCqAQtnd3Mtd2l6LWltZ8ABAQ&sclient=img&ei=LhW8Y4SYGI6I0PEPl9egoAs
=======================================
cell division stages
https://www.google.ca/search?q=cell+division+stages&tbm=isch&ved=2ahUKEwiRn8-Ly7r8AhUUMH0KHSbFAGUQ2-cCegQIABAA&oq=cell+division&gs_lcp=CgNpbWcQARgDMgQIIxAnMgQIIxAnMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgUIABCABDIECAAQQzIECAAQQ1AAWABg62hoAHAAeACAAbwCiAG8ApIBAzMtMZgBAKoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=qBW8Y5GrBJTg9AOmioOoBg
============================
cell division mitosis and meiosis
https://www.google.ca/search?q=cell+division+mitosis+and+meiosis&tbm=isch&ved=2ahUKEwiRn8-Ly7r8AhUUMH0KHSbFAGUQ2-cCegQIABAA&oq=cell+division&gs_lcp=CgNpbWcQARgEMgQIIxAnMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgQIABBDMgUIABCABDIECAAQQzIECAAQQ1AAWABggY8CaABwAHgAgAFpiAGoAZIBAzEuMZgBAKoBC2d3cy13aXotaW1nwAEB&sclient=img&ei=qBW8Y5GrBJTg9AOmioOoBg
=====================================================================================================
RiboNucleic Acid(리보핵산]-[mRNA(전령messenger설계]*[리보솜 Ribosomal RNA, rRNA합성] (Transter RNA tRNA운반체]
=============================================================================
3종류의 RNA:
전령 RNA(Messenger RNA, mRNA): 단백질의 설계도
리보솜 RNA(Ribosomal RNA, rRNA): 단백질 합성장소
운반 RNA(Transter RNA, tRNA): 아미노산의 운반체
=======================================
https://namu.wiki/w/%EC%83%9D%EB%AA%85
====================================
https://ko.wikipedia.org/wiki/%EC%83%9D%EB%AA%85#:~:text=%EC%83%9D%EB%AA%85(%E7%94%9F%E5%91%BD)%20%EB%98%90%EB%8A%94%20%EC%82%B6%EC%9D%80%20%EC%83%9D%EB%AC%BC,%ED%99%95%EC%8B%A4%EC%B9%98%20%EC%95%8A%EC%95%84%20%EA%B3%84%EC%86%8D%20%EB%85%BC%EC%9F%81%20%EC%A4%91%EC%9D%B4%EB%8B%A4.
================================
生命 / life
생물들이 가지고 있는 특성으로 생물이 살아서 숨쉬고 활동할 수 있게 하는 힘을 말한다. 생명력은 항상성을 포함한 여러가지 의미로 쓰인다. 생명에 대한 일반적인 과학적 정의는 생물 문서에 나와 있다. 또 다른 관점에서는 외부나 전체의 엔트로피 증가를 가속화하여 자신의 엔트로피를 낮추거나, 유지하는 개체로 보기도 한다. 이러한 주장은 에르빈 슈뢰딩거의 저서 '생명이란 무엇인가?'에서 제기된 것을 계기로 대중화되었으며 사회유기체설과도 관계가 있다. 인간을 비롯한 모든 생명은 죽으면 무기체로 돌아간다.
애시당초 생물이라는 것 자체가 분류의 하나이기에 생물학적인 관점에서도 아주 명확한 정의는 없다. 보통 아래의 특성을 전부 가지거나 대부분 가지고 있는 개체는 생명으로 본다.
1) 생식과 유전
2) 세포로 이루어짐
3) 물질대사
4) 자극에 대한 반응, 항상성
5) 적응과 진화
6) 발생과 생장
바이러스는 유전물질을 가지고 증식을 하여[2] 자연선택에 의한 진화도 하지만 물질대사[3]와 세포체 구조의 부족 때문에 일반적으로는 생명으로 간주되지 않는다
=====================================
생명
위키백과, 우리 모두의 백과사전.
생명(生命) 또는 삶은 생물이 태어나서 죽기 전까지의 과정 및 상태를 말하나 학술적으로 생과 사의 경계는 확실치 않아 계속 논쟁 중이다.
다양한 생물계 수준.
Magnify-clip.png
생물 분류의 계급의 주요 8개 순위. 사소한 중간 순위는 표시하지 않음. 밑으로 갈수록 더 좁은 범위의 계급.
생명의 정의
생명이란 자체 신호를 가지고 스스로를 유지할 수 있는 물체를, 그러한 기능이 종료되었거나 (죽음) 또는 그러한 기능이 없어 비활성체로 분류되었거나를 막론하고 그렇지 않은 것과를 구별짓는 특성이다. 생물학적으로 볼 때, 생명체는 다음과 같은 특성을 지니지만 엄밀하지는 않다.
물질대사에 바탕을 둔 정의
생장한다.
물질대사를 한다.
외부적으로나 내부적으로 움직인다.
자신과 닮은 개체를 생산해 내는 생식기능이 있다.
외부 자극에 반응한다.
위의 기준을 엄밀하게 적용한다면 다음과 같은 문제가 생긴다.
불이 살아있다고 할 수 있다.
노새는 생식 능력이 없으므로 살아있다고 할 수 없다.(그러나 노새의 세포 하나하나는 분열할 수 있다)
바이러스는 성장하지 않고 숙주세포 바깥에서는 생식을 할 수 없으므로 살아있다고 할 수 없다.
지구상의 생명체를 연구하는 생물학자들은 살아있는 생명체가 다음과 같은 현상을 보인다고 한다.
살아있는 생명체는 탄수화물, 지질, 핵산, 단백질과 같은 성분을 지니고 있다.
살아있는 생명체는 살아가기 위해 에너지와 물질을 모두 필요로 한다.
살아있는 생명체는 하나나 그 이상의 세포로 이루어져 있다.
살아있는 생명체는 항상성을 유지한다.
살아있는 생명체의 종은 진화한다.
지구상의 생명체는 모두 탄소로 이루어진 유기체로 이루어져 있다. 어떤 사람들은 이런 점이 모든 우주의 모든 생명체에도 해당한다고 보지만, 다른 이들은 이 현상을 '탄소 쇼비니즘'이라고 부른다.
살아있는 생명체는 호흡을 해야 한다
생화학적(분자생물학적) 정의
생물(生物): 생명이 있는 것
생물을 구성하는 생화학적 분자들
단백질
지방(지질, 지방산)
탄수화물
핵산(DNA, RNA)
효소반응: 단백질로 만들어진 생체 촉매
핵산
DNA
<nowiki /> 이 부분의 본문은 DNA입니다.
Deoxyribonucleic acid(디옥시리보핵산)
생명의 청사진
후손에게 전해지는 유전물질(예외: retrovirus)
Wiki letter w.svg 이 문단은 아직 미완성입니다.
RNA
대개 mRNA(messenger RNA)를 가리킴
Ribonucleic acid(리보핵산)
단백질 합성의 청사진
3종류의 RNA:
전령 RNA(Messenger RNA, mRNA): 단백질의 설계도
리보솜 RNA(Ribosomal RNA, rRNA): 단백질 합성장소
운반 RNA(Transter RNA, tRNA): 아미노산의 운반체
현대생물학의 기본 패러다임: 분자생물학
<nowiki /> 이 부분의 본문은 분자생물학입니다.
단백질의 효소와 생합성을 지배하는 디옥시리보핵산 또는 디엔에이(DNA)의 구조와 특성을 바탕으로, 중요한 생명현상을 설명하려는 생물학의 한 분야이다. 분자생물학의 발달은 1940년대에 DNA가 유전자의 본체임이 밝혀지고, 동시에 DNA의 유전정보가 RNA를 통하여 세포질 속에서 단백질 합성을 지배한다는 사실이 차츰 알려지게 되었다. 더욱이 1953년 J.D.웟슨과 F.H.C.크릭에 의하여 DNA의 이중나선구조의 모형이 제출됨에 이르러 새로운 단계를 맞이하였다. 그 후, 분자생물학의 주류는 DNA의 복제 및 단백질의 생합성을 중심으로 하여 유전의 본질 및 유전의 메커니즘을 설명하고, 나아가서 생물체의 조절작용이나 진화의 현상을 설명하는 것으로 되었다. 따라서, 분자생물학의 중심이 되는 것은 분자유전학으로 볼 수 있다. 그러나 근육의 기본이 되는 수축단백질인 액토미오신이라는 단백질의 분자구조를 바탕으로 근육의 수축운동을 설명한다든지, 뇌에 있어서의 기억의 기작을 단백질이나 RNA의 미세한 구조의 변화로 설명하려는 일 등도 분자생물학에 포함시키고 있다.
유전학적 정의
다윈의 <종의 기원>
<nowiki /> 이 부분의 본문은 종의 기원입니다.
영국의 생물학자 찰스 다윈(1809년~1882년)의 생물의 진화론에 관한 저서로서, 1859년 11월 런던의 존 머리사(John Murray社)에서 간행하였다. 다윈은 1858년 7월 1일 린네 학회에서 A.R.월리스와 함께 진화론의 논문을 발표하고 나서, 요약 형식으로 이 책을 간행하였다. 전문 14장으로 구성되고, 변이(變異)의 법칙·생존경쟁·본능·잡종(雜種)·화석(化石)·지리적 분포·분류학 및 발생학 등의 여러 면에서 자연선택을 전개하고 있다. 1872년에 간행된 제6판이 최종판인데, 이때 과학적으로 제기된 여러 이론(異論)에 답한 새로운 한 장(章)이 제7장으로 추가되었다.
W.페리의 자연신학(自然神學)의 토대였던 적응의 현상에 자연적 설명을 부여하려는 것이 이 책을 간행하게 된 목표 중의 하나였다. 간행 직후부터 종교계의 심한 공격을 받았으나, 약 10년만에 생물학계에서 확고한 지위를 획득하였다.
멘델의 유전법칙
<nowiki /> 이 부분의 본문은 멘델의 유전법칙입니다.
그레고어 멘델(G.J. Mendel)이 완두콩을 이용한 교배 실험을 통해서 밝혀낸 유전법칙. 1865년에 처음 발표되어 유전학을 만들어 내는 계기가 되었다 멘델 이전에는 유전 현상을 설명하기 위해서, 정자와 난자 속에 있는 액체가 섞여서 부모의 특징이 이어진다는 혼합 이론을 사용하였다. 이 이론에 대항하여 멘델은 부모의 특성, 즉 형질을 결정하는 것은 단위로 환원할 수 있는 물질이라는 것을 밝혀 냈다. 멘델 스스로는 여기에 따로 이름을 붙이지 않았지만 이것이 바로 유전자이다. 즉 멘델은 그의 법칙을 통해 유전자 개념을 처음 과학적으로 확립한 셈이다. 그러나 당초 1865년에 멘델이 처음 이 법칙을 발표했을 때에는 크게 주목 받지 못했다. 하지만 그 성과가 완전히 묻힌 것은 아니고, 다른 학자들의 논문에서도 멘델에 대한 언급을 볼 수 있었으며 1881년에 나온 브리태니커 백과사전에도 멘델의 연구가 소개되어 있었다. 그러다 1900년에 코렌스(C. Correns), 체르마크(E.V. Tschermak), 드 브리스(H. de Vries)가 유사한 연구를 하다가 동일한 시기에 멘델의 연구를 다시 발견하여 세상에 알려지게 되었다. 이 중에서 코렌스가 멘델의 연구 성과에 "멘델의 법칙"이라는 이름을 붙였다.
멘델의 연구
멘델은 자신의 연구를 위해서 완두콩을 그 재료로 사용했다. 우선 완두콩을 잘 키워서 키가 큰 완두콩과 키가 작은 완두콩을 서로 분리해 낸다. 이렇게 키가 큰 것과 작은 것이 각각 완두콩의 형질이 된다. 키가 큰 것은 큰 것대로 따로 키우고 작은 것은 작은 것대로 따로 키워서, 몇 세대 후에는 무조건 키가 큰 종자와 무조건 키가 작은 종자를 얻는다. 이 완두콩들을 서로 교배를 시켰더니 키가 큰 완두콩이 나오는 종자만을 얻을 수 있었다. 기존 발상으로는 키가 큰 것과 작은 것의 중간 키 정도가 되는 완두콩이 나와야 했는데 그렇지 않은 결과가 나온 것이다. 이런 식으로 한 가지 형질만이 겉으로 드러나는 것을 우열의 법칙이라고 하며, 이때 나타나게 되는 키가 큰 형질을 우성, 반대로 나타나지 않는 키가 작은 형질을 열성이라고 한다. 다음에는 이렇게 얻은 완두콩을 자가수분을 거쳐 다시 키워 보았다. 그러자 키가 큰 완두콩과 작은 완두콩의 비율이 3대 1로 나타났다. 이를 분리의 법칙이라고 한다. 또한 멘델은 완두콩의 키 이외에도 다른 형질로도 실험을 했다. 둥근 완두콩과 주름진 완두콩, 그리고 녹색 완두콩과 노란 완두콩에서도 같은 결과를 얻을 수 있었다. 더군다나 이러한 서로 다른 형질은 상관관계가 없이 서로 독립적으로 우열의 법칙과 분리의 법칙을 나타냈다. 이것을 독립의 법칙이라고 한다. 이 세 가지가 바로 멘델의 법칙이다.
멘델의 재발견
멘델의 법칙은 1884년 멘델이 사망한 후 16년 동안 빛을 보지 못하고 있다가 1900년에 와서 세 명의 연구자에 의해 다시 발견되었다. 네덜란드의 드 브리스는 1890년대에 달맞이꽃을 가지고 독자적인 실험을 해서 멘델의 법칙을 발견했으며 1895년에 멘델에 대해서 알게 되었다. 독일의 코렌스는 완두콩으로 실험을 해서 1899년에 멘델의 법칙을 다시 발견했으며 이때 멘델의 논문을 다시 읽어보았다고 한다. 그 후 멘델과 같은 실험을 했다는 사실에 논문 발표를 꺼리고 있다가 1900년에 드 브리스가 발표하기 직전의 논문에 멘델에 대한 언급이 없는 것을 보고 멘델을 소개하기 위해 "멘델의 법칙"이라는 논문을 썼다. 사실 드 브리스의 논문에는 멘델에 대한 언급이 있었지만 번역하는 도중에 빠졌다고 한다. 마지막으로 체르마크는 오스트리아에서 역시 완두콩을 가지고 연구하고 있었으며 드 브리스의 논문을 보고 급히 자신의 논문을 투고하여, 세 사람의 논문은 같이 게재되었다.
멘델 법칙의 한계와 발전
멘델의 법칙은 매우 훌륭한 이론이었으나 이후 연구가 계속되어 유전이 어떻게 이루어지는가를 더욱 잘 알게 된 이후에는 한정적인 상황에서만 성립한다는 사실이 알려지게 되었다. 우선 독립의 법칙은, 해당 형질을 나타내는 유전자들이 서로 다른 염색체에 있을 때에만 성립한다. 이것은 멘델이 매우 운이 좋았음을 알 수 있는 부분이기도 하다. 왜냐하면 완두콩의 상동염색체는 모두 7쌍({\displaystyle 2n=14}{\displaystyle 2n=14})이며, 멘델이 확인한 7개의
======================================================
유전자-JENE- DNA - The Genetic material for all forms of life on earth
DNA https://en.wikipedia.org/wiki/DNA
https://ko.wikipedia.org/wiki/%EC%9C%A0%EC%A0%84%EC%9E%90
===========================================================
유전자는 모든 생물의 고유한 특성에 대한 정보를 담고 있는 부분으로 다음 세대로 전해지는 물질로 DNA(디옥시리보핵산/Deoxyribo Nucleic Acid)서열 중에 특정 의미를 갖는 부분입니다.
위키백과, 우리 모두의 백과사전.
염색체(오른쪽 위)는 DNA가 실타래처럼 감겨 있는 구조로 되어 있다. 유전자는 DNA의 이중 나선 한 구간을 차지하
유전자란 - 수산·해양 LMO 안전성센터 - 국립수산과학원https://www.nifs.go.kr › lmo › lmo › lmo4_11
•
Feedback
유전자 - 나무위키https://namu.wiki › 유전자
·
Translate this page
Oct 12, 2022 — 자가 복제가 되는 성질의 분자 조합물이자 부모가 자식에게 특성을 물려주는 현상인 유전을 일으키는 단위이다. 건물을 짓기 위해 설계도가 필요하듯, ...
이기적 유전자 · 유전자 검사 · DNA
유전자 - 위키백과, 우리 모두의 백과사전https://ko.wikipedia.org › wiki › 유...
·
Translate this page
유전자(遺傳子, 영어: gene)는 유전의 기본단위이다. 지구상의 모든 생물은 유전자를 지니고 있다. 유전자에는 생물의 세포를 구성하고 유지하고, 이것들이 유기적인 ...
유전자 발현 · 유전자 이동 · 유전자형 · 위유전자
유전자와 염색체 - 기초 - MSD 매뉴얼 - 일반인용https://www.msdmanuals.com › 유전학
·
Translate this page
유전자형(또는 유전체)은 사람의 고유한 유전자 조합이나 유전자 구조를 의미합니다. 따라서 유전자형은 사람의 신체가 단백질을 합성하는 기제뿐 아니라 해당 신체가 구축 ...
유전자와 검사 | 유전학이란 | 의학유전학강좌 - 서울아산병원https://www.amc.seoul.kr › content
·
Translate this page
유전자는 DNA로 구성된 유전정보단위로서, 세포의 생명현상을 유지하고 특정한 기능을 수행하는데 필요한 모든 단백질을 만들기 위해 완벽한 명령체제를 지시 전달하는 ...
일반적 개요 · 암유전자검사는 현재 어느 단계... · 유전자검사의 위험요인은 무엇...
유전자(gene) | 알기쉬운의학용어 | 의료정보 - 서울아산병원https://amc.seoul.kr › easymediterm
·
Translate this page
유전자란 유전 형질을 나타내는 원인이 되는 인자입니다. 부모의 특징이 다음 세대인 자식에게 나타날 때, 그 특징을 만들어내는 인자로 유전 정보의 기본 단위를 말합니다 ...
유전자는 어떻게 우리 몸의 모양과 기능을 만들어낼까?https://www.sciencetimes.co.kr › news
·
Translate this page
Apr 9, 2021 — 유전자는 우리 몸을 이루는 세포의 핵 속에 있다. 세포핵에는 DNA가 있는데, 이 DNA에 유전자가 있다. DNA의 기본 단위는 염기와 당, 인산이 결합한 ...
유전자 - 위키낱말사전https://ko.wiktionary.org › wiki › 유...
·
Translate this page
1. 유전 형질을 지닌 단위, 염기서열 속에 들어있다. 번역. 그리스
======================================
The largest scientific study of its kind estimates that Earth could play host to more than 1 trillion different species, which means we've probably only identified a vanishingly small proportion of them – only about one-thousandth of 1 percent.
life forms -- 5.6 million species
A life form or lifeform is an entity that is living.[1][2]
Estimates on the number of Earth's current species range from 10 million to 14 million,[3] of which about 1.2 million have been documented and over 86 percent have not yet been described.[4] More recently, in May 2016, scientists reported that 1 trillion species are estimated to be on Earth currently with only one-thousandth of one percent described.[5]
More than 99% of all species, amounting to over five billion species,[6] that ever lived on Earth are estimated to be extinct.[7][8]
Frohttps://en.wikipedia.org/wiki/Genem Wikipedia, the free encyclopedia
Jump to: navigation, search
This article is about the heritable unit for transmission of biological traits. For other uses, see Gene (disambiguation).
Chromosome
(107 - 1010 bp)
DNA
Gene
(103 - 106 bp )
Function
A gene is a region of DNA that encodes function. A chromosome consists of a long strand of DNA containing many genes. A human chromosome can have up to 500 million base pairs of DNA with thousands of genes.
A gene is a sequence of DNA or RNA which codes for a molecule that has a function. The DNA is first copied into RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission of genes to an organism's offspring is the basis of the inheritance of phenotypic traits. These genes make up different DNA sequences called genotypes. Genotypes along with environmental and developmental factors determine what the phenotypes will be. Most biological traits are under the influence of polygenes (many different genes) as well as gene–environment interactions. Some genetic traits are instantly visible, such as eye color or number of limbs, and some are not, such as blood type, risk for specific diseases, or the thousands of basic biochemical processes that comprise life.
Genes can acquire mutations in their sequence, leading to different variants, known as alleles, in the population. These alleles encode slightly different versions of a protein, which cause different phenotypical traits. Usage of the term "having a gene" (e.g., "good genes," "hair colour gene") typically refers to containing a different allele of the same, shared gene. Genes evolve due to natural selection or survival of the fittest of the alleles.
The concept of a gene continues to be refined as new phenomena are discovered.[1] For example, regulatory regions of a gene can be far removed from its coding regions, and coding regions can be split into several exons. Some viruses store their genome in RNA instead of DNA and some gene products are functional non-coding RNAs. Therefore, a broad, modern working definition of a gene is any discrete locus of heritable, genomic sequence which affect an organism's traits by being expressed as a functional product or by regulation of gene expression.[2][3]
The term gene was introduced by Danish botanist, plant physiologist and geneticist Wilhelm Johannsen in 1905.[4] It is inspired by the ancient Greek: γόνος, gonos, that means offspring and procreation.
Contents [hide]
1
History
1.1
Discovery of discrete inherited units
1.2
Discovery of DNA
1.3
Modern synthesis and its successors
2
Molecular basis
2.1
DNA
2.2
Chromosomes
3
Structure and function
3.1
Structure
3.2
Functional definitions
4
Gene expression
4.1
Genetic code
4.2
Transcription
4.3
Translation
4.4
Regulation
4.5
RNA genes
5
Inheritance
5.1
Mendelian inheritance
5.2
DNA replication and cell division
5.3
Molecular inheritance
6
Molecular evolution
6.1
Mutation
6.2
Sequence homology
6.3
Origins of new genes
7
Genome
7.1
Number of genes
7.2
Essential genes
7.3
Genetic and genomic nomenclature
8
Genetic engineering
9
See also
10
References
10.1
Main textbook
10.2
References
10.3
Further reading
11
External links
History[edit]
Gregor Mendel
Main article: History of genetics
Discovery of discrete inherited units[edit]
The existence of discrete inheritable units was first suggested by Gregor Mendel (1822–1884).[5] From 1857 to 1864, in Brno (Czech Republic), he studied inheritance patterns in 8000 common edible pea plants, tracking distinct traits from parent to offspring. He described these mathematically as 2n combinations where n is the number of differing characteristics in the original peas. Although he did not use the term gene, he explained his results in terms of discrete inherited units that give rise to observable physical characteristics. This description prefigured Wilhelm Johannsen's distinction between genotype (the genetic material of an organism) and phenotype (the visible traits of that organism). Mendel was also the first to demonstrate independent assortment, the distinction between dominant and recessive traits, the distinction between a heterozygote and homozygote, and the phenomenon of discontinuous inheritance.
Prior to Mendel's work, the dominant theory of heredity was one of blending inheritance, which suggested that each parent contributed fluids to the fertilisation process and that the traits of the parents blended and mixed to produce the offspring. Charles Darwin developed a theory of inheritance he termed pangenesis, from Greek pan ("all, whole") and genesis ("birth") / genos ("origin").[6][7] Darwin used the term gemmule to describe hypothetical particles that would mix during reproduction.
Mendel's work went largely unnoticed after its first publication in 1866, but was rediscovered in the late 19th century by Hugo de Vries, Carl Correns, and Erich von Tschermak, who (claimed to have) reached similar conclusions in their own research.[8] Specifically, in 1889, Hugo de Vries published his book Intracellular Pangenesis,[9] in which he postulated that different characters have individual hereditary carriers and that inheritance of specific traits in organisms comes in particles. De Vries called these units "pangenes" (Pangens in German), after Darwin's 1868 pangenesis theory.
Sixteen years later, in 1905, Wilhelm Johannsen introduced the term 'gene'[4] and William Bateson that of 'genetics'[10] while Eduard Strasburger, amongst others, still used the term 'pangene' for the fundamental physical and functional unit of heredity.[11]
Discovery of DNA[edit]
Advances in understanding genes and inheritance continued throughout the 20th century. Deoxyribonucleic acid (DNA) was shown to be the molecular repository of genetic information by experiments in the 1940s to 1950s.[12][13] The structure of DNA was studied by Rosalind Franklin and Maurice Wilkins using X-ray crystallography, which led James D. Watson and Francis Crick to publish a model of the double-stranded DNA molecule whose paired nucleotide bases indicated a compelling hypothesis for the mechanism of genetic replication.[14][15]
In the early 1950s the prevailing view was that the genes in a chromosome acted like discrete entities, indivisible by recombination and arranged like beads on a string. The experiments of Benzer using mutants defective in the rII region of bacteriophage T4 (1955-1959) showed that individual genes have a simple linear structure and are likely to be equivalent to a linear section of DNA.[16][17]
Collectively, this body of research established the central dogma of molecular biology, which states that proteins are translated from RNA, which is transcribed from DNA. This dogma has since been shown to have exceptions, such as reverse transcription in retroviruses. The modern study of genetics at the level of DNA is known as molecular genetics.
In 1972, Walter Fiers and his team at the University of Ghent were the first to determine the sequence of a gene: the gene for Bacteriophage MS2 coat protein.[18] The subsequent development of chain-termination DNA sequencing in 1977 by Frederick Sanger improved the efficiency of sequencing and turned it into a routine laboratory tool.[19] An automated version of the Sanger method was used in early phases of the Human Genome Project.[20]
Modern synthesis and its successors[edit]
Main article: Modern synthesis (20th century)
The theories developed in the early 20th century to integrate Mendelian genetics with Darwinian evolution are called the modern synthesis, a term introduced by Julian Huxley.[21]
Evolutionary biologists have subsequently modified this concept, such as George C. Williams' gene-centric view of evolution. He proposed an evolutionary concept of the gene as a unit of natural selection with the definition: "that which segregates and recombines with appreciable frequency."[22]:24 In this view, the molecular gene transcribes as a unit, and the evolutionary gene inherits as a unit. Related ideas emphasizing the centrality of genes in evolution were popularized by Richard Dawkins.[23][24]
Molecular basis[edit]
Main article: DNA
The chemical structure of a four base pair fragment of a DNA double helix. The sugar-phosphate backbone chains run in opposite directions with the bases pointing inwards, base-pairing A to T and C to G with hydrogen bonds.
DNA[edit]
The vast majority of living organisms encode their genes in long strands of DNA (deoxyribonucleic acid). DNA consists of a chain made from four types of nucleotide subunits, each composed of: a five-carbon sugar (2'-deoxyribose), a phosphate group, and one of the four bases adenine, cytosine, guanine, and thymine.[25]:2.1
Two chains of DNA twist around each other to form a DNA double helix with the phosphate-sugar backbone spiralling around the outside, and the bases pointing inwards with adenine base pairing to thymine and guanine to cytosine. The specificity of base pairing occurs because adenine and thymine align to form two hydrogen bonds, whereas cytosine and guanine form three hydrogen bonds. The two strands in a double helix must therefore be complementary, with their sequence of bases matching such that the adenines of one strand are paired with the thymines of the other strand, and so on.[25]:4.1
Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose; this is known as the 3' end of the molecule. The other end contains an exposed phosphate group; this is the 5' end. The two strands of a double-helix run in opposite directions. Nucleic acid synthesis, including DNA replication and transcription occurs in the 5'→3' direction, because new nucleotides are added via a dehydration reaction that uses the exposed 3' hydroxyl as a nucleophile.[26]:27.2
The expression of genes encoded in DNA begins by transcribing the gene into RNA, a second type of nucleic acid that is very similar to DNA, but whose monomers contain the sugar ribose rather than deoxyribose. RNA also contains the base uracil in place of thymine. RNA molecules are less stable than DNA and are typically single-stranded. Genes that encode proteins are composed of a series of three-nucleotide sequences called codons, which serve as the "words" in the genetic "language". The genetic code specifies the correspondence during protein translation between codons and amino acids. The genetic code is nearly the same for all known organisms.[25]:4.1
Chromosomes[edit]
Fluorescent microscopy image of a human female karyotype, showing 23 pairs of chromosomes . The DNA is stained red, with regions rich in housekeeping genes further stained in green. The largest chromosomes are around 10 times the size of the smallest.[27]
The total complement of genes in an organism or cell is known as its genome, which may be stored on one or more chromosomes. A chromosome consists of a single, very long DNA helix on which thousands of genes are encoded.[25]:4.2 The region of the chromosome at which a particular gene is located is called its locus. Each locus contains one allele of a gene; however, members of a population may have different alleles at the locus, each with a slightly different gene sequence.
The majority of eukaryotic genes are stored on a set of large, linear chromosomes. The chromosomes are packed within the nucleus in complex with storage proteins called histones to form a unit called a nucleosome. DNA packaged and condensed in this way is called chromatin.[25]:4.2 The manner in which DNA is stored on the histones, as well as chemical modifications of the histone itself, regulate whether a particular region of DNA is accessible for gene expression. In addition to genes, eukaryotic chromosomes contain sequences involved in ensuring that the DNA is copied without degradation of end regions and sorted into daughter cells during cell division: replication origins, telomeres and the centromere.[25]:4.2 Replication origins are the sequence regions where DNA replication is initiated to make two copies of the chromosome. Telomeres are long stretches of repetitive sequence that cap the ends of the linear chromosomes and prevent degradation of coding and regulatory regions during DNA replication. The length of the telomeres decreases each time the genome is replicated and has been implicated in the aging process.[28] The centromere is required for binding spindle fibres to separate sister chromatids into daughter cells during cell division.[25]:18.2
Prokaryotes (bacteria and archaea) typically store their genomes on a single large, circular chromosome. Similarly, some eukaryotic organelles contain a remnant circular chromosome with a small number of genes.[25]:14.4 Prokaryotes sometimes supplement their chromosome with additional small circles of DNA called plasmids, which usually encode only a few genes and are transferable between individuals. For example, the genes for antibiotic resistance are usually encoded on bacterial plasmids and can be passed between individual cells, even those of different species, via horizontal gene transfer.[29]
Whereas the chromosomes of prokaryotes are relatively gene-dense, those of eukaryotes often contain regions of DNA that serve no obvious function. Simple single-celled eukaryotes have relatively small amounts of such DNA, whereas the genomes of complex multicellular organisms, including humans, contain an absolute majority of DNA without an identified function.[30] This DNA has often been referred to as "junk DNA". However, more recent analyses suggest that, although protein-coding DNA makes up barely 2% of the human genome, about 80% of the bases in the genome may be expressed, so the term "junk DNA" may be a misnomer.[3]
Structure and function[edit]
Structure[edit]
Regulatory sequence
Regulatory sequence
Enhancer
/silencer
Promoter
5'UTR
Open reading frame
3'UTR
Enhancer
/silencer
Proximal
Core
Start
Stop
Terminator
Transcription
DNA
Exon
Exon
Exon
Intron
Intron
Post-transcriptional
modification
Pre-
mRNA
Protein coding region
5'cap
Poly-A tail
Translation
Mature
mRNA
Protein
The structure of a eukaryotic protein-coding gene. Regulatory sequence controls when and where expression occurs for the protein coding region (red). Promoter and enhancer regions (yellow) regulate the transcription of the gene into a pre-mRNA which is modified to remove introns (light grey) and add a 5' cap and poly-A tail (dark grey). The mRNA 5' and 3' untranslated regions (blue) regulate translation into the final protein product.[31]
Polycistronic operon
Regulatory sequence
Regulatory sequence
Enhancer
Enhancer
/silencer
/silencer
Operator
Promoter
5'UTR
ORF
ORF
UTR
3'UTR
Start
Start
Stop
Stop
Terminator
Transcription
DNA
RBS
RBS
Protein coding region
Protein coding region
mRNA
Translation
Protein
The structure of a prokaryotic operon of protein-coding genes. Regulatory sequence controls when expression occurs for the multiple protein coding regions (red). Promoter, operator and enhancer regions (yellow) regulate the transcription of the gene into an mRNA. The mRNA untranslated regions (blue) regulate translation into the final protein products.[31]
The structure of a gene consists of many elements of which the actual protein coding sequence is often only a small part. These include DNA regions that are not transcribed as well as untranslated regions of the RNA.
Flanking the open reading frame, genes contain a regulatory sequence that is required for their expression. First, genes require a promoter sequence. The promoter is recognized and bound by transcription factors and RNA polymerase to initiate transcription.[25]:7.1 The recognition typically occurs as a consensus sequence like the TATA box. A gene can have more than one promoter, resulting in messenger RNAs (mRNA) that differ in how far they extend in the 5' end.[32] Highly transcribed genes have "strong" promoter sequences that form strong associations with transcription factors, thereby initiating transcription at a high rate. Others genes have "weak" promoters that form weak associations with transcription factors and initiate transcription less frequently.[25]:7.2 Eukaryotic promoter regions are much more complex and difficult to identify than prokaryotic promoters.[25]:7.3
Additionally, genes can have regulatory regions many kilobases upstream or downstream of the open reading frame that alter expression. These act by binding to transcription factors which then cause the DNA to loop so that the regulatory sequence (and bound transcription factor) become close to the RNA polymerase binding site.[33] For example, enhancers increase transcription by binding an activator protein which then helps to recruit the RNA polymerase to the promoter; conversely silencers bind repressor proteins and make the DNA less available for RNA polymerase.[34]
The transcribed pre-mRNA contains untranslated regions at both ends which contain a ribosome binding site, terminator and start and stop codons.[35] In addition, most eukaryotic open reading frames contain untranslated introns which are removed before the exons are translated. The sequences at the ends of the introns, dictate the splice sites to generate the final mature mRNA which encodes the protein or RNA product.[36]
Many prokaryotic genes are organized into operons, with multiple protein-coding sequences that are transcribed as a unit.[37][38] The genes in an operon are transcribed as a continuous messenger RNA, referred to as a polycistronic mRNA. The term cistron in this context is equivalent to gene. The transcription of an operon’s mRNA is often controlled by a repressor that can occur in an active or inactive state depending on the presence of certain specific metabolites.[39] When active, the repressor binds to a DNA sequence at the beginning of the operon, called the operator region, and represses transcription of the operon; when the repressor is inactive transcription of the operon can occur (see e.g. Lac operon). The products of operon genes typically have related functions and are involved in the same regulatory network.[25]:7.3
Functional definitions[edit]
Defining exactly what section of a DNA sequence comprises a gene is difficult.[1] Regulatory regions of a gene such as enhancers do not necessarily have to be close to the coding sequence on the linear molecule because the intervening DNA can be looped out to bring the gene and its regulatory region into proximity. Similarly, a gene's introns can be much larger than its exons. Regulatory regions can even be on entirely different chromosomes and operate in trans to allow regulatory regions on one chromosome to come in contact with target genes on another chromosome.[40][41]
Early work in molecular genetics suggested the concept that one gene makes one protein. This concept (originally called the one gene-one enzyme hypothesis) emerged from an influential 1941 paper by George Beadle and Edward Tatum on experiments with mutants of the fungus Neurospora crassa.[42] Norman Horowitz, an early colleague on the Neurospora research, reminisced in 2004 that “these experiments founded the science of what Beadle and Tatum called biochemical genetics. In actuality they proved to be the opening gun in what became molecular genetics and all the developments that have followed from that.”[43] The one gene-one protein concept has been refined since the discovery of genes that can encode multiple proteins by alternative splicing and coding sequences split in short section across the genome whose mRNAs are concatenated by trans-splicing.[3][44][45]
A broad operational definition is sometimes used to encompass the complexity of these diverse phenomena, where a gene is defined as a union of genomic sequences encoding a coherent set of potentially overlapping functional products.[10] This definition categorizes genes by their functional products (proteins or RNA) rather than their specific DNA loci, with regulatory elements classified as gene-associated regions.[10]
Gene expression[edit]
Main article: Gene expression
In all organisms, two steps are required to read the information encoded in a gene's DNA and produce the protein it specifies. First, the gene's DNA is transcribed to messenger RNA (mRNA).[25]:6.1 Second, that mRNA is translated to protein.[25]:6.2 RNA-coding genes must still go through the first step, but are not translated into protein.[46] The process of producing a biologically functional molecule of either RNA or protein is called gene expression, and the resulting molecule is called a gene product.
Genetic code[edit]
Schematic of a single-stranded RNA molecule illustrating a series of three-base codons. Each three-nucleotide codon corresponds to an amino acid when translated to protein
The nucleotide sequence of a gene's DNA specifies the amino acid sequence of a protein through the genetic code. Sets of three nucleotides, known as codons, each correspond to a specific amino acid.[25]:6 The principle that three sequential bases of DNA code for each amino acid was demonstrated in 1961 using frameshift mutations in the rIIB gene of bacteriophage T4[47] (see Crick, Brenner et al. experiment).
Additionally, a "start codon", and three "stop codons" indicate the beginning and end of the protein coding region. There are 64 possible codons (four possible nucleotides at each of three positions, hence 43 possible codons) and only 20 standard amino acids; hence the code is redundant and multiple codons can specify the same amino acid. The correspondence between codons and amino acids is nearly universal among all known living organisms.[48]
Transcription[edit]
Transcription produces a single-stranded RNA molecule known as messenger RNA, whose nucleotide sequence is complementary to the DNA from which it was transcribed.[25]:6.1 The mRNA acts as an intermediate between the DNA gene and its final protein product. The gene's DNA is used as a template to generate a complementary mRNA. The mRNA matches the sequence of the gene's DNA coding strand because it is synthesised as the complement of the template strand. Transcription is performed by an enzyme called an RNA polymerase, which reads the template strand in the 3' to 5' direction and synthesizes the RNA from 5' to 3'. To initiate transcription, the polymerase first recognizes and binds a promoter region of the gene. Thus, a major mechanism of gene regulation is the blocking or sequestering the promoter region, either by tight binding by repressor molecules that physically block the polymerase, or by organizing the DNA so that the promoter region is not accessible.[25]:7
In prokaryotes, transcription occurs in the cytoplasm; for very long transcripts, translation may begin at the 5' end of the RNA while the 3' end is still being transcribed. In eukaryotes, transcription occurs in the nucleus, where the cell's DNA is stored. The RNA molecule produced by the polymerase is known as the primary transcript and undergoes post-transcriptional modifications before being exported to the cytoplasm for translation. One of the modifications performed is the splicing of introns which are sequences in the transcribed region that do not encode protein. Alternative splicing mechanisms can result in mature transcripts from the same gene having different sequences and thus coding for different proteins. This is a major form of regulation in eukaryotic cells and also occurs in some prokaryotes.[25]:7.5[49]
Translation[edit]
Protein coding genes are transcribed to an mRNA intermediate, then translated to a functional protein. RNA-coding genes are transcribed to a functional non-coding RNA. (PDB: 3BSE, 1OBB, 3TRA)
Translation is the process by which a mature mRNA molecule is used as a template for synthesizing a new protein.[25]:6.2 Translation is carried out by ribosomes, large complexes of RNA and protein responsible for carrying out the chemical reactions to add new amino acids to a growing polypeptide chain by the formation of peptide bonds. The genetic code is read three nucleotides at a time, in units called codons, via interactions with specialized RNA molecules called transfer RNA (tRNA). Each tRNA has three unpaired bases known as the anticodon that are complementary to the codon it reads on the mRNA. The tRNA is also covalently attached to the amino acid specified by the complementary codon. When the tRNA binds to its complementary codon in an mRNA strand, the ribosome attaches its amino acid cargo to the new polypeptide chain, which is synthesized from amino terminus to carboxyl terminus. During and after synthesis, most new proteins must fold to their active three-dimensional structure before they can carry out their cellular functions.[25]:3
Regulation[edit]
Genes are regulated so that they are expressed only when the product is needed, since expression draws on limited resources.[25]:7 A cell regulates its gene expression depending on its external environment (e.g. available nutrients, temperature and other stresses), its internal environment (e.g. cell division cycle, metabolism, infection status), and its specific role if in a multicellular organism. Gene expression can be regulated at any step: from transcriptional initiation, to RNA processing, to post-translational modification of the protein. The regulation of lactose metabolism genes in E. coli (lac operon) was the first such mechanism to be described in 1961.[50]
RNA genes[edit]
A typical protein-coding gene is first copied into RNA as an intermediate in the manufacture of the final protein product.[25]:6.1 In other cases, the RNA molecules are the actual functional products, as in the synthesis of ribosomal RNA and transfer RNA. Some RNAs known as ribozymes are capable of enzymatic function, and microRNA has a regulatory role. The DNA sequences from which such RNAs are transcribed are known as non-coding RNA genes.[46]
Some viruses store their entire genomes in the form of RNA, and contain no DNA at all.[51][52] Because they use RNA to store genes, their cellular hosts may synthesize their proteins as soon as they are infected and without the delay in waiting for transcription.[53] On the other hand, RNA retroviruses, such as HIV, require the reverse transcription of their genome from RNA into DNA before their proteins can be synthesized. RNA-mediated epigenetic inheritance has also been observed in plants and very rarely in animals.[54]
Inheritance[edit]
Inheritance of a gene that has two different alleles (blue and white). The gene is located on an autosomal chromosome. The white allele is recessive to the blue allele. The probability of each outcome in the children's generation is one quarter, or 25 percent.
Main articles: Mendelian inheritance and Heredity
Organisms inherit their genes from their parents. Asexual organisms simply inherit a complete copy of their parent's genome. Sexual organisms have two copies of each chromosome because they inherit one complete set from each parent.[25]:1
Mendelian inheritance[edit]
According to Mendelian inheritance, variations in an organism's phenotype (observable physical and behavioral characteristics) are due in part to variations in its genotype (particular set of genes). Each gene specifies a particular trait with different sequence of a gene (alleles) giving rise to different phenotypes. Most eukaryotic organisms (such as the pea plants Mendel worked on) have two alleles for each trait, one inherited from each parent.[25]:20
Alleles at a locus may be dominant or recessive; dominant alleles give rise to their corresponding phenotypes when paired with any other allele for the same trait, whereas recessive alleles give rise to their corresponding phenotype only when paired with another copy of the same allele. If you know the genotypes of the organisms, you can determine which alleles are dominant and which are recessive. For example, if the allele specifying tall stems in pea plants is dominant over the allele specifying short stems, then pea plants that inherit one tall allele from one parent and one short allele from the other parent will also have tall stems. Mendel's work demonstrated that alleles assort independently in the production of gametes, or germ cells, ensuring variation in the next generation. Although Mendelian inheritance remains a good model for many traits determined by single genes (including a number of well-known genetic disorders) it does not include the physical processes of DNA replication and cell division.[55][56]
DNA replication and cell division[edit]
The growth, development, and reproduction of organisms relies on cell division; the process by which a single cell divides into two usually identical daughter cells. This requires first making a duplicate copy of every gene in the genome in a process called DNA replication.[25]:5.2 The copies are made by specialized enzymes known as DNA polymerases, which "read" one strand of the double-helical DNA, known as the template strand, and synthesize a new complementary strand. Because the DNA double helix is held together by base pairing, the sequence of one strand completely specifies the sequence of its complement; hence only one strand needs to be read by the enzyme to produce a faithful copy. The process of DNA replication is semiconservative; that is, the copy of the genome inherited by each daughter cell contains one original and one newly synthesized strand of DNA.[25]:5.2
The rate of DNA replication in living cells was first measured as the rate of phage T4 DNA elongation in phage-infected E. coli and found to be impressively rapid.[57] During the period of exponential DNA increase at 37 °C, the rate of elongation was 749 nucleotides per second.
After DNA replication is complete, the cell must physically separate the two copies of the genome and divide into two distinct membrane-bound cells.[25]:18.2 In prokaryotes (bacteria and archaea) this usually occurs via a relatively simple process called binary fission, in which each circular genome attaches to the cell membrane and is separated into the daughter cells as the membrane invaginates to split the cytoplasm into two membrane-bound portions. Binary fission is extremely fast compared to the rates of cell division in eukaryotes. Eukaryotic cell division is a more complex process known as the cell cycle; DNA replication occurs during a phase of this cycle known as S phase, whereas the process of segregating chromosomes and splitting the cytoplasm occurs during M phase.[25]:18.1
Molecular inheritance[edit]
The duplication and transmission of genetic material from one generation of cells to the next is the basis for molecular inheritance, and the link between the classical and molecular pictures of genes. Organisms inherit the characteristics of their parents because the cells of the offspring contain copies of the genes in their parents' cells. In asexually reproducing organisms, the offspring will be a genetic copy or clone of the parent organism. In sexually reproducing organisms, a specialized form of cell division called meiosis produces cells called gametes or germ cells that are haploid, or contain only one copy of each gene.[25]:20.2 The gametes produced by females are called eggs or ova, and those produced by males are called sperm. Two gametes fuse to form a diploid fertilized egg, a single cell that has two sets of genes, with one copy of each gene from the mother and one from the father.[25]:20
During the process of meiotic cell division, an event called genetic recombination or crossing-over can sometimes occur, in which a length of DNA on one chromatid is swapped with a length of DNA on the corresponding homologous non-sister chromatid. This can result in reassortment of otherwise linked alleles.[25]:5.5 The Mendelian principle of independent assortment asserts that each of a parent's two genes for each trait will sort independently into gametes; which allele an organism inherits for one trait is unrelated to which allele it inherits for another trait. This is in fact only true for genes that do not reside on the same chromosome, or are located very far from one another on the same chromosome. The closer two genes lie on the same chromosome, the more closely they will be associated in gametes and the more often they will appear together; genes that are very close are essentially never separated because it is extremely unlikely that a crossover point will occur between them. This is known as genetic linkage.[58]
Molecular evolution[edit]
Main article: Molecular evolution
Mutation[edit]
DNA replication is for the most part extremely accurate, however errors (mutations) do occur.[25]:7.6 The error rate in eukaryotic cells can be as low as 10−8 per nucleotide per replication,[59][60] whereas for some RNA viruses it can be as high as 10−3.[61] This means that each generation, each human genome accumulates 1–2 new mutations.[61] Small mutations can be caused by DNA replication and the aftermath of DNA damage and include point mutations in which a single base is altered and frameshift mutations in which a single base is inserted or deleted. Either of these mutations can change the gene by missense (change a codon to encode a different amino acid) or nonsense (a premature stop codon).[62] Larger mutations can be caused by errors in recombination to cause chromosomal abnormalities including the duplication, deletion, rearrangement or inversion of large sections of a chromosome. Additionally, DNA repair mechanisms can introduce mutational errors when repairing physical damage to the molecule. The repair, even with mutation, is more important to survival than restoring an exact copy, for example when repairing double-strand breaks.[25]:5.4
When multiple different alleles for a gene are present in a species's population it is called polymorphic. Most different alleles are functionally equivalent, however some alleles can give rise to different phenotypic traits. A gene's most common allele is called the wild type, and rare alleles are called mutants. The genetic variation in relative frequencies of different alleles in a population is due to both natural selection and genetic drift.[63] The wild-type allele is not necessarily the ancestor of less common alleles, nor is it necessarily fitter.
Most mutations within genes are neutral, having no effect on the organism's phenotype (silent mutations). Some mutations do not change the amino acid sequence because multiple codons encode the same amino acid (synonymous mutations). Other mutations can be neutral if they lead to amino acid sequence changes, but the protein still functions similarly with the new amino acid (e.g. conservative mutations). Many mutations, however, are deleterious or even lethal, and are removed from populations by natural selection. Genetic disorders are the result of deleterious mutations and can be due to spontaneous mutation in the affected individual, or can be inherited. Finally, a small fraction of mutations are beneficial, improving the organism's fitness and are extremely important for evolution, since their directional selection leads to adaptive evolution.[25]:7.6
Sequence homology[edit]
A sequence alignment, produced by ClustalO, of mammalian histone proteins
Genes with a most recent common ancestor, and thus a shared evolutionary ancestry, are known as homologs.[64] These genes appear either from gene duplication within an organism's genome, where they are known as paralogous genes, or are the result of divergence of the genes after a speciation event, where they are known as orthologous genes,[25]:7.6 and often perform the same or similar functions in related organisms. It is often assumed that the functions of orthologous genes are more similar than those of paralogous genes, although the difference is minimal.[65][66]
The relationship between genes can be measured by comparing the sequence alignment of their DNA.[25]:7.6 The degree of sequence similarity between homologous genes is called conserved sequence. Most changes to a gene's sequence do not affect its function and so genes accumulate mutations over time by neutral molecular evolution. Additionally, any selection on a gene will cause its sequence to diverge at a different rate. Genes under stabilizing selection are constrained and so change more slowly whereas genes under directional selection change sequence more rapidly.[67] The sequence differences between genes can be used for phylogenetic analyses to study how those genes have evolved and how the organisms they come from are related.[68][69]
Origins of new genes[edit]
Evolutionary fate of duplicate genes.
The most common source of new genes in eukaryotic lineages is gene duplication, which creates copy number variation of an existing gene in the genome.[70][71] The resulting genes (paralogs) may then diverge in sequence and in function. Sets of genes formed in this way comprise a gene family. Gene duplications and losses within a family are common and represent a major source of evolutionary biodiversity.[72] Sometimes, gene duplication may result in a nonfunctional copy of a gene, or a functional copy may be subject to mutations that result in loss of function; such nonfunctional genes are called pseudogenes.[25]:7.6
"Orphan" genes, whose sequence shows no similarity to existing genes, are less common than gene duplicates. Estimates of the number of genes with no homologs outside humans range from 18[73] to 60.[74] Two primary sources of orphan protein-coding genes are gene duplication followed by extremely rapid sequence change, such that the original relationship is undetectable by sequence comparisons, and de novo conversion of a previously non-coding sequence into a protein-coding gene.[75] De novo genes are typically shorter and simpler in structure than most eukaryotic genes, with few if any introns.[70] Over long evolutionary time periods, de novo gene birth may be responsible for a significant fraction of taxonomically-restricted gene families.[76]
Horizontal gene transfer refers to the transfer of genetic material through a mechanism other than reproduction. This mechanism is a common source of new genes in prokaryotes, sometimes thought to contribute more to genetic variation than gene duplication.[77] It is a common means of spreading antibiotic resistance, virulence, and adaptive metabolic functions.[29][78] Although horizontal gene transfer is rare in eukaryotes, likely examples have been identified of protist and alga genomes containing genes of bacterial origin.[79][80]
Genome[edit]
The genome is the tot
- 이전글Atom **우리몸은소금 한알 *원자*전자 *우리몸의 원자수는 10^28승/ *양자콤퓨터 *과학 발전 역사 23.05.09
- 다음글**Neuron신경세포 **감정을 느끼는 이유 **정서(emotion** BRAIN 뇌 생각 원리 23.01.09
댓글목록
등록된 댓글이 없습니다.