Name: the genetic code and codons
Uploaded: 2020-09-24T15:06:53.000Z
Duration: 3 min 6 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Life Sciences

from-molecules-to-organisms-structures-and-processes

From Molecules To Organisms: Structures And Processes

HS-LS1-1

From DNA to Protein

DNA에는 유전자, 뉴클레오티드 서열이 포함되어 있으며 그중 일부는 단백질에서 일련의 아미노산을 코딩하는 명령입니다. DNA에서 RNA로의 단백질의 유전 정보의 흐름은 센트럴 도그마로 알려진 과정입니다. 이 과정의 첫 번째 단계는 RNA 중합효소가 RNA 기반 복제 또는 유전자의 전사체를 합성하는 전사 과정입니다.

DNA는 전사체에 추가된 각 새로운 RNA 염기가 DNA의 원래 가닥에 대해 상보적인 주형으로 사용됩니다. 메신저 또는 mRNA라고 불리우는 일부 전사체는 단백질을 코딩하며 코딩되지 않은 전사체는 다른 세포 과정에 참여합니다. 예를 들어 리보솜 rRNA 및 전달 tRNA는 단백질 합성에 참여합니다.

다음 단계는 번역과정이며 여기서 mRNA가 해독되어 아미노산 사슬을 합성합니다. 유전자 코드로 알려진 일련의 명령이 mRNA를 읽는 데 사용됩니다. 대부분의 유기체는 특정한 아미노산으로 번역하는 코돈이라고 불리우는 세 개의 뉴클레오티드 그룹으로 구성된 동일한 범용 코드를 사용합니다.

64개의 다른 뉴클레오티드 트리플렛이 있지만 코드를 퇴화시키는 단백질에는 20개의 표준 아미노산만 있습니다. 즉 여러 코돈 집합이 동일한 명령을 줄 수 있습니다. 61개의 집합은 아미노산을 암호화하고 3개는 번역의 중지를 알립니다.

번역은 rRNA와 단백질의 대형 복합체인 리보솜에서 tRNA의 도움으로 발생합니다. tRNA는 3개의 헤어핀 루프 구조를 가지고 있습니다. 하나의 루프에는 코돈에 대해 상보적 염기를 가지는 안티코돈이라는 서열이 있습니다.

이 서열에 해당하는 아미노산은 tRNA의 끝에 부착되어 리보솜으로 전달합니다. 개시인자라고 불리는 단백질은 작은 리보솜 단위, 개시 tRNA 및 mRNA를 결합합니다. 복합체가 조립된 후 리보솜은 번역 시작 위치를 찾기 위해 mRNA를 따라 나갑니다.

여기서 개시 tRNA 안티코돈이 상보적 코돈에 결합합니다. 큰 리보솜 단위가 조립체에 결합되여 번역이 시작됩니다. 다음 tRNA가 들어오면 개시제에서 나온 아미노산이 분리되고 인접한 아미노산으로 옮겨져 폴리펩티드 사슬이 성장합니다.

아미노산의 추가는 mRNA에서 정지코돈이 검출될 때까지 계속됩니다. 그 다음 리보솜은 사슬을 풀어 기능성 단백질로 접힐 수 있습니다.

dna에서 단백질까지

DNA에서 mRNA, 단백질로 세포 내 유전 정보의 흐름은 유전자가 mRNA의 순서를 지정하고, 다시 모든 단백질을 구성하는 아미노산의 순서를 지정한다는 중심 교리로 설명됩니다. 한 분자를 다른 분자로 해독하는 것은 특정 단백질과 RNA에 의해 수행됩니다. DNA에 저장된 정보는 세포 기능의 핵심이기 때문에 세포가 DNA 자체를 손상시키지 않고 보호하면서 단백질 합성을 위해 이 정보의 mRNA 복사본을 만드는 것이 직관적으로 이해됩니다. DNA를 RNA로 복사하는 것은 상대적으로 간단하며, DNA 가닥에서 읽은 모든 뉴클레오티드에 대해 하나의 뉴클레오티드가 mRNA 가닥에 추가됩니다. 단백질로의 번역은 3개의 mRNA 뉴클레오티드가 폴리펩티드 서열의 하나의 아미노산에 해당하기 때문에 좀 더 복잡합니다. 그러나 단백질로의 번역은 여전히 체계적이고 공선적이어서 뉴클레오티드 1~3은 아미노산 1에 해당하고, 뉴클레오티드 4~6은 아미노산 2에 해당합니다.

유전자 코드는 퇴화되고 보편적이다

각 아미노산은 삼중항 코돈이라고 불리는 3개의 뉴클레오티드 서열로 정의됩니다. mRNA와 단백질 "알파벳"의 "문자" 수가 다르기 때문에 과학자들은 단일 아미노산이 뉴클레오티드의 조합으로 표시되어야 한다는 이론을 세웠습니다. 2개의 뉴클레오티드 조합이 가능한 경우는 16개뿐이므로 뉴클레오티드 이중선은 모든 아미노산을 지정하는 데 충분하지 않습니다(4_2). 대조적으로, 64개의 가능한 뉴클레오티드 삼중항(4_3개)이 있는데, 이는 아미노산의 수보다 훨씬 많습니다. 과학자들은 아미노산이 세 개의 뉴클레오티드로 암호화되어 있으며 유전 암호가 "퇴화"되어 있다는 이론을 세웠습니다. 즉, 주어진 아미노산은 하나 이상의 뉴클레오티드 삼중항에 의해 암호화될 수 있습니다. 이것은 나중에 실험적으로 확인되었습니다. Francis Crick과 Sydney Brenner는 화학적 돌연변이 유발 물질인 프로플라빈을 사용하여 바이러스 유전자에 1개, 2개 또는 3개의 뉴클레오티드를 삽입했습니다. 1개 또는 2개의 뉴클레오티드가 삽입되면 정상적인 단백질이 생성되지 않습니다. 세 개의 뉴클레오티드가 삽입되면 단백질이 합성되고 기능하게 됩니다. 이는 아미노산이 세 개의 뉴클레오티드 그룹으로 지정되어야 함을 입증했습니다. 이러한 뉴클레오티드 삼중항을 코돈이라고 합니다. 하나 또는 두 개의 뉴클레오티드를 삽입하면 삼중항 판독 프레임이 완전히 바뀌어 이후의 모든 아미노산에 대한 메시지가 변경됩니다. 3개의 뉴클레오티드를 삽입하면 번역 중에 추가 아미노산이 삽입되지만 나머지 단백질의 무결성은 유지되었습니다.

폴리펩티드 사슬에 특정 아미노산을 추가하도록 지시하는 코돈 외에도 64개의 코돈 중 3개가 단백질 합성을 종결하고 번역 기계에서 폴리펩티드를 방출합니다. 이러한 삼중항을 넌센스 코돈 또는 정지 코돈이라고 합니다. 또 다른 코돈인 AUG도 특별한 기능을 가지고 있습니다. 아미노산 메티오닌을 지정하는 것 외에도 번역을 시작하는 시작 코돈 역할도 합니다. 번역을 위한 판독 프레임은 mRNA의 5' 말단 근처에 있는 AUG 시작 코돈에 의해 설정됩니다. 시작 코돈 다음에 mRNA는 정지 코돈을 만날 때까지 3개의 그룹으로 읽혀집니다.

여러 개의 유사한 코돈에 의한 단일 아미노산의 지정을 "축퇴"라고 합니다. 퇴화는 무작위 돌연변이의 부정적인 영향을 줄이기 위한 세포 메커니즘으로 여겨집니다. 동일한 아미노산을 지정하는 코돈은 일반적으로 하나의 뉴클레오티드만 다릅니다. 또한, 화학적으로 유사한 측쇄를 가진 아미노산은 유사한 코돈에 의해 암호화됩니다. 예를 들어, GA* 블록을 차지하는 아스파테이트(Asp)와 글루타메이트(Glu)는 모두 음전하를 띠고 있습니다. 유전자 코드의 이러한 미묘한 차이는 단일 뉴클레오티드 치환 돌연변이가 동일한 아미노산을 지정하지만 효과가 없거나 유사한 아미노산을 지정하여 단백질이 완전히 기능하지 않게 되는 것을 방지할 수 있음을 보장합니다.

유전암호는 거의 보편적입니다. 몇 가지 사소한 예외를 제외하면 거의 모든 종은 단백질 합성에 동일한 유전암호를 사용합니다. 코돈 보존은 말의 글로빈 단백질을 암호화하는 정제된 mRNA가 튤립 세포로 전달될 수 있고 튤립이 말 글로빈을 합성할 수 있음을 의미합니다. 단 하나의 유전자 코드가 있다는 것은 지구상의 모든 생명체가 공통의 기원을 공유한다는 강력한 증거입니다. 특히 20개의 아미노산과 64개의 삼중 코돈의 조합이 약 10^84개 가능하다는 점을 고려하면 더욱 그렇습니다.

이 문서는 에서 발췌되었습니다 <a href="https://openstax.org/books/biology-2e/pages/15-1-the-genetic-code">Openstax, Biology 2e, Chapter 15.1: </a><a href="https://openstax.org/books/biology-2e/pages/15-1-the-genetic-code">The Genetic Code</a>.

DNA에서 단백질까지

DNA에서 mRNA로, 단백질로 가는 세포의 유전 정보의 흐름은 유전자가 다음의 서열을 지정한다고 명시한 중앙 교리에 의해 설명됩니다.

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the genetic code and codons

The genetic code and codons explain how cells turn DNA information into proteins. Genes first direct the sequence of mRNA, and mRNA then directs the sequence of amino acids that make up proteins. Specific proteins and RNAs carry out this decoding. Cells copy DNA into mRNA so the original DNA stays protected while the cell uses the message for protein synthesis.

Copying DNA to RNA is relatively simple. One nucleotide is added to the mRNA strand for every nucleotide read on the DNA strand. Translating mRNA into protein is more complex because three mRNA nucleotides correspond to one amino acid. Even so, the process is orderly and stays collinear. Nucleotides 1 to 3 specify amino acid 1, nucleotides 4 to 6 specify amino acid 2, and the pattern continues in the same way.

Each amino acid is defined by a three-nucleotide codon, also called a triplet codon. Scientists proposed this idea because the mRNA and protein alphabets are different sizes. Two-nucleotide combinations would not be enough, since there are only 16 possible doublets. Three-nucleotide combinations provide 64 possible triplets, which is far more than the number of amino acids. This led to the idea that the code is degenerate, meaning one amino acid can be encoded by more than one codon.

Francis Crick and Sydney Brenner tested this idea with the chemical mutagen proflavin. They inserted one, two, or three nucleotides into a virus gene. Inserting one or two nucleotides prevented normal proteins from being made. Inserting three nucleotides still allowed a functional protein to be synthesized. This showed that amino acids are read in groups of three. One- or two-nucleotide insertions shift the reading frame and change every later amino acid, while a three-nucleotide insertion adds one amino acid but preserves the rest of the protein.

Some codons do not add amino acids. Three of the 64 codons are stop codons, also called nonsense codons, and they end protein synthesis. Another codon, AUG, has two roles. It codes for methionine and also acts as the start codon that begins translation. The AUG start codon near the 5' end of the mRNA sets the reading frame. After that, the mRNA is read in groups of three until a stop codon appears.

Degeneracy may help reduce the effects of random mutations. Codons that specify the same amino acid usually differ by only one nucleotide. Amino acids with similar side chains are also often encoded by similar codons. For example, aspartate and glutamate are both negatively charged and fall in the GA* codon block. This means a single-nucleotide substitution may have no effect, or it may lead to a similar amino acid instead of a harmful change.

The genetic code is nearly universal. With a few minor exceptions, most species use the same code to make proteins. This shared code means a purified mRNA for horse globin could be placed in a tulip cell, and the tulip would make horse globin. The near-universal code is also strong evidence that life on Earth shares a common origin, especially since there are about 10^84 possible combinations of 20 amino acids and 64 triplet codons.

The Genetic Code and Codons

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from dna to protein

The genetic code and codons explain how cells turn DNA information into proteins. Genes first direct the sequence of mRNA, and mRNA then directs the sequence of amino acids that make up proteins. Specific proteins and RNAs carry out this decoding. Cells copy DNA into mRNA so the original DNA stays protected while the cell uses the message for protein synthesis. Copying DNA to RNA is relatively simple. One nucleotide is added to the mRNA strand for every nucleotide read on the DNA strand.

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key terms and concepts

Learn how codons, stop signals, and the AUG start codon guide protein synthesis, and why the genetic code is nearly universal across species.

The Genetic Code and Codons | JoVE K12

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Structure and Function

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DNA Base Pairing

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The flow of genetic information in cells from DNA to mRNA to protein is described by the central dogma, which states that genes specify the sequence of ...

The DNA Helix

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The central dogma explains the flow of genetic information from DNA nucleotides to the amino acid sequence of proteins.
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Overview

Deoxyribonucleic acid, or DNA, is the genetic material responsible for passing traits from generation to generation in all organisms and most ...

DNA Packaging

Overview

Eukaryotes have large genomes compared to prokaryotes. In order to fit their genomes into a cell, eukaryotes must pack their DNA tightly inside ...

RNA Structure

Overview
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RNA Stability

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Types of RNA

Overview
Three main types of RNA are involved in protein synthesis: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). These RNAs ...

DNA as a Genetic Template

What is Gene Expression?

A gene is a stretch of DNA that serves as the blueprint for functional RNAs and proteins. Since DNA is comprised&#160; of nucleotides and proteins are ...

Transcription

Transcription is the synthesis of RNA from a DNA sequence by RNA polymerase. It is the first step in producing a protein from a gene sequence. ...

Translation

Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following transcription, it constitutes ...

Ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

tRNA Activation

Initiation of Translation

Termination of Translation

What are Cells?

Cell Diversity

The concept of a cell started with microscopic observations of dead cork tissue by Robert Hooke in 1665. Hooke coined the term &#34;cell&#34; based on the ...

Cells of the Epidermis

The epidermis is made of four or five layers of epithelial cells, depending on its location in the body. From deep to superficial, these layers are the ...

Bone Cells and Tissue

Bones contain a relatively small number of cells entrenched in a matrix of organic and inorganic components. Although bone cells compose only a small ...

Gross Anatomy of Skeletal Muscles

The connective tissues play a significant role in arranging the muscle fibers into a hierarchical structure that forms a complete muscle. Consider a ...

Structure of Cardiac Muscles

Cardiac muscle, or myocardium, is a specialized type of muscle found exclusively in the heart. Its unique structural and functional characteristics enable ...

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Structure and Organization of Smooth Muscles

In the human body, smooth muscle tissue is found lining the visceral and tubular organs such as the liver, lungs, blood vessels, and respiratory tract.
...

Chromosome Replication

Before a cell can divide, it must accurately replicate all of its chromosomes, including the DNA and its associated histone and non-histone ...

Neurons: The Cell Body and the Dendrites

A typical nerve cell comprises three main components: the cell body, dendrites, and the axon. The cell body, also known as the soma or perikaryon, serves ...

Lampbrush Chromosomes

In 1882, Flemming observed lampbrush chromosomes (LBC) in salamander eggs. Later in 1892, R&#252;ckert observed LBCs in shark egg cells and coined the ...

Neurons: The Axon

The axon is a long, thin extended portion of the neuron that carries impulses from its cell body toward the effector cell.
Axoplasm, the axon&#39;s ...

Polytene Chromosomes

Polytene chromosomes are giant interphase chromosomes with several DNA strands placed side by side. They were discovered in the year 1881 by Balbiani in ...

Nervous Tissue: Neuron Types

Neurons, the fundamental units of the nervous system, can be classified based on both their structural and functional characteristics.
Structurally, ...

Euchromatin

The extent of chromatin compaction can be studied by staining chromatin using specific DNA binding dyes. Under the microscope, the dense-compacted regions ...

Nervous Tissue: Glial Cells

Glial cells or neuroglia are non-neuronal cells in the nervous system that outnumber neurons. These include astrocytes, oligodendrocytes, microglia, and ...

Heterochromatin

Lymphoid Cells and Tissues

Lymphoid cells and lymphoid tissues are the two major components of lymphoid organs.
Lymphoid cells consist of immune system cells such as B and T ...

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Chromatin Position Affects Gene Expression

Chromatin is the massive complex of DNA and proteins packaged inside the nucleus. The complexity of chromatin folding and how it is packaged inside the ...

Two structural features of the DNA molecule provide a basis for the mechanisms of heredity: the four nucleotide bases and its double-stranded nature. The ...

Organization of Genes

Chromosome Structure

A functional eukaryotic chromosome must contain three elements: a centromere, telomeres, and numerous origins of replication.
The centromere is a DNA ...

Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells. Emphasis is on the conceptual understanding that DNA sequences determine the amino acid sequence and thus protein structure. Students can produce scientific writing, or presentations, and/or physical models that communicate constructed explanations.

Characteristics of Life

Biology is a natural science that studies life and living organisms, including their structure, function, development, interactions, evolution, ...

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Levels of Organization

Biological organization is the classification of biological structures, ranging from atoms at the bottom of the hierarchy to the Earth&#x27;s biosphere. ...

The Scientific Method

The scientific method is a detailed, empirical problem-solving process used by biologists and other scientists. This iterative approach involves ...

Taxonomy

Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics. It uses a hierarchy of increasingly ...

Phylogeny

Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon ...

Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms. Emphasis is on functions at the organism system level such as nutrient uptake, water delivery, or organism movement in response to neural stimuli. An example of an interacting system could be an artery depending on the proper function of elastic tissue and smooth muscle to regulate and deliver the proper amount of blood within the circulatory system.

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Overview of Metabolism

Living cells constantly carry out various chemical reactions which are necessary for their proper functioning. These reactions are interlinked to one ...

Regulation of Metabolism

Cellular needs and conditions vary from cell to cell and change within individual cells over time. For example, the required enzymes and energetic demands ...

Positive and Negative Feedback Loops

Animal organs and organ systems constantly adjust to internal and external changes through a process called homeostasis (&#34;steady state&#34;). Examples ...

Functions of Life

Human life is characterized by a variety of functions that are essential for survival and well-being. These functions include metabolism, movement, ...

Requirements for Human Life

The Earth and its atmosphere have provided humans with air, water, and food, but these are not the only requirements for survival. Humans also require a ...

What is Homeostasis?

Maintaining homeostasis requires that the body continuously maintain its internal conditions. Each physiological condition has a particular set point, ...

Negative and Positive Feedback

Homeostatic Imbalance

Homeostasis is the maintenance of a stable internal environment within the body, which is crucial for the proper functioning of cells, tissues, organs, ...

pH Homeostasis

Acid-base homeostasis is essential for maintaining normal physiological activities in humans. The pH of various body fluids is strictly regulated because ...

homeostatic-imbalances-in-body-temperature

Homeostatic Imbalances in Body Temperature

Hyperthermia is an umbrella term for elevated body temperature that occurs when heat production exceeds the body&#39;s ability to dissipate it.
...

Regulation of Food Intake

The hypothalamus releases peptides influencing feeding behavior.
Two hypothalamic neuronal groups participate in this process.
Neuropeptide Y (NPY) and ...

Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis in living organisms. Examples of investigations could include heart rate responses to exercise, stomate responses to moisture and temperature, root development in response to water levels, or cell response to hypertonic and hypotonic environments.

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What is the Cell Cycle?

The cell cycle refers to the sequence of events occurring throughout a typical cell&#8217;s life. In eukaryotic cells, the somatic cell cycle has two ...

Interphase

The cell cycle occurs over approximately 24 hours (in a typical human cell) and in two distinct stages: interphase, which includes three phases of the ...

The Cell Cycle Control System

Positive Regulator Molecules

Inhibition of CDK Activity

S-Cdk Initiates DNA Replication

M-Cdk Drives Transition Into Mitosis

Mitogens and the Cell Cycle

Replicative Cell Senescence

Use a model to illustrate the role of the cell cycle and differentiation in producing and maintaining complex organisms. Emphasis is on conceptual understanding that mitosis passes on genetically identical materials via replication, not on the details of each phase in mitosis.

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The Genetic Code and Codons

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