Name: how mutations change dna
Uploaded: 2020-11-23T11:47:33.000Z
Duration: 1 min 39 s
Channel: JoVE

K12 Standards

Tennessee Academic Standards

High School

Biology

Heredity

BIO1.LS3.2

Mutations

- 点突变，即单个核苷酸的改变
 
 可以产生完全正常
 
 或者安全无用的蛋白质，取决于改变的类型
 
 这些包括：沉默突变，错义突变，无义突变
 
 和移码突变
 
 沉默突变，顾名思义
 
 对蛋白质的氨基酸序列没有影响
 
 例如，如果密码子CCA变成CCG
 
 它仍会编码氨基酸，脯氨酸
 
 蛋白质仍将正常工作
 
 而错义突变，在另一方面
 
 会导致一种氨基酸取代另一种
 
 比如精氨酸代替脯氨酸
 
 这将导致蛋白质无法正常工作
 
 无义突变发生在一个氨基酸的密码子
 
 变为终止密码子时
 
 这向细胞发出停止翻译的信号
 
 导致蛋白质过早被截断
 
 常常不能正常工作
 
 最后，移码突变发生在
 
 读码框架
 
 即一套三个核苷酸如何组合成密码子
 
 被移位，这常常是因为插入或删除
 
 了一个或多个核苷酸
 
 这会形成一系列
 
 编码不同氨基酸的新密码子
 
 产生不正常的蛋白质

突变

突变是DNA序列的改变。这些变化可以自发发生，也可以由环境因素引起。突变可以用多种不同的方式来描述：它们是否和如何改变蛋白质的氨基酸序列，它们是否发生在小面积或大面积的DNA上，它们是否发生在体细胞或生殖细胞中。

<h4>分子水平上点突变的后果</h4>
 
发生在单个核苷酸上的突变称为点突变。当基因内发生点突变时，后果的严重程度可能会因编码的氨基酸序列的变化而不同。沉默突变不会改变氨基酸的特性，也不会对生物体产生影响。错义突变改变了单一氨基酸，如果改变了蛋白质的功能，这种影响可能会很严重。无义突变产生一个终止密码子，截断蛋白质，很可能使其失去功能。当一个或多个核苷酸插入或从编码蛋白质的DNA序列中删除时，发生移码突变，影响突变位置下游的所有密码子。
 
<h4>染色体改变是大规模的突变</h4>
 
最剧烈的突变，染色体改变，改变了染色体的物理结构。染色体的改变可以包括单个染色体中大段DNA的缺失、复制或反转，或者不同染色体的一部分整合。这些突变通常比点突变严重得多，因为它们包含许多基因和调控元件。染色体改变可以通过对受影响的细胞进行核型分析来检测。
 
<h4>只有种系突变是遗传的</h4>
 
突变可以发生在任何细胞中，但只有存在于卵细胞和精子细胞中的生殖系突变才能传播给后代。例如，遗传性疾病是由有害的生殖系突变引起的遗传性疾病的一个亚型。它们可以是常染色体，发生在1到22号染色体上，也可以是性连锁的，发生在X或Y染色体上。遗传性疾病的一个例子是囊性纤维化(CF)，一种主要影响肺部的疾病。它是由基因内的一个缺失引起的，该缺失从 CFTR 蛋白中除去一个氨基酸。CF是一种常染色体隐性遗传病，意味着拥有一个突变的基因拷贝和一个正常拷贝的人不会发展成这种疾病；其它疾病，如亨廷顿病（一种神经退行性疾病）是常染色体显性遗传病，意味着只有一个突变的基因拷贝是疾病发展所必需的。
 
<h4>有些突变是由环境因素引起的</h4>
 
体细胞突变和种系突变都可以在DNA复制过程中自发发生，但也可能是由于暴露于环境中的辐射或化学物质所致。破坏DNA并引起突变的外部因素称为诱变剂。一种特性良好的环境诱变剂是紫外线(UV) 辐射。紫外线辐射比可见光携带更多的能量，并通过破坏碱基对之间的键来破坏DNA，从而导致同一DNA链上的胸腺嘧啶碱基在特征胸腺嘧啶二聚体中彼此配对。太阳是紫外线的自然来源。最具破坏性的波长， UV-C在大气中被截获，但是 UV-A 和 UV-B射线到达地球表面。紫外线暴露的人工来源包括晒植被，它主要用少量的紫外线-B来传播紫外线-A。幸运的是，细胞有修复受损DNA的机制，但有时在快速分裂的细胞（如皮肤细胞）中，损伤在细胞分裂前无法修复。如果DNA损伤发生在对细胞生长和分裂有重要调节作用的基因组区域，如果不加以修复，就可能导致癌症。

概述

突变是指DNA序列发生的变化。这些变化可自发产生，也可由暴露于环境因素而诱发。...

Education

教育

JoVE Core

Molecular Biology

分子生物学

Unit 1

第一单元

DNA, Cells, and Evolution

DNA、细胞与进化

KEY TERMS AND CONCEPTS

关键术语与概念

how mutations change dna

Mutations are changes in DNA. They can alter the genetic code and affect how genes work. In high school biology, students often study mutations to understand how DNA changes can influence traits.

The transcript focuses on two common mutation types: point mutations and frameshift mutations. A point mutation changes one nucleotide, which is one DNA building block. A frameshift mutation happens when nucleotides are added or removed and the reading frame shifts.

These changes matter because they can change the way genetic information is read. Some mutations may have little effect, while others can change the resulting protein. Understanding point mutations and frameshift mutations helps explain how DNA variation is linked to cell function and inherited change.

How Mutations Change DNA

the dna helix

DNA Structure and Base Pairing

DNA has a helical structure that helps store genetic information. The double helix is the shape formed by two strands that twist around each other. This structure is a key feature of DNA in cells. The two strands are held together by base pairing. Bases on one strand match with bases on the other strand in a regular way. This pairing helps keep the DNA molecule stable and organized. The helix shape also helps explain how DNA fits into chromosomes and carries instructions for living things. By...

the central dogma

DNA to Protein: Central Dogma Steps

The central dogma explains how genetic information moves from DNA to RNA to protein. This flow is a key idea in molecular biology. It helps show how cells use genes to make the molecules that carry out work. DNA stores the instructions for making proteins. During transcription, a gene in DNA is copied into RNA. The RNA then carries that message to the next stage. In translation, the RNA message is used to build a protein. Proteins do much of the cell’s work, so this process connects genes to...

prokaryotic cells

Inside Prokaryotic Cell Structure

Prokaryotic cells have a simple internal structure compared with many other cells. They are usually divided into two groups: bacteria and archaea. These cells have no nucleus, so their DNA is not enclosed in a membrane-bound compartment. Instead, the genetic material is found in the nucleoid, a region where the DNA is located in the cell. Some prokaryotic cells also contain plasmids, which are small extra DNA molecules. A capsule may surround the cell and provide an additional outer layer. <br...

eukaryotic compartmentalization

Cell Compartments in Eukaryotes

Eukaryotic cells use compartments to organize many different jobs inside one cell. These compartments help separate processes so they can happen in the right place. The compartment called the cytosol is the fluid part of the cell. It surrounds the other internal structures and helps support many cell processes. Inside the cell, membrane-bound organelles create distinct microenvironments. A microenvironment is a small internal space with conditions that fit a specific task. This separation...

the tree of life - bacteria, archaea, eukaryotes

the-tree-of-life-bacteria-archaea-eukaryotes

How Life Is Classified Into Three Domains

The tree of life shows how organisms are related through evolution. Its root represents the common ancestor of all life on Earth. From that point, branches spread out like a tree. The tips of the branches represent living, or extant, species. Species that no longer exist, called extinct species, appear closer to the center of the tree. Today, these organisms are grouped into three domains: bacteria, archaea, and eukaryotes. Scientists still debate these divisions, so the tree of life keeps...

mutations

Mutations are changes in DNA. They can alter the genetic code and affect how genes work. In high school biology, students often study mutations to understand how DNA changes can influence traits. The transcript focuses on two common mutation types: point mutations and frameshift mutations. A point mutation changes one nucleotide, which is one DNA building block. A frameshift mutation happens when nucleotides are added or removed and the reading frame shifts. These changes matter because they...

gene evolution - fast or slow?

Why Some Gene Regions Evolve Faster

Gene regions do not all change at the same rate. In eukaryotes, long stretches of DNA do not code for proteins or RNAs. Some of these non-coding regions include important regulatory sequences, but most have no known function. Because little or no selection pressure acts on them, they often change the fastest over evolutionary time. Protein-coding regions usually evolve more slowly. A change in a coding sequence can alter a protein and make it less effective at doing its job. That creates...

genome size and the evolution of new genes

genome-size-and-the-evolution-of-new-genes

How Genome Size Shapes New Genes

Genome size can vary widely, and it also helps show how new genes form. Every living organism has a genome, whether it uses RNA or DNA. Yet the size of that genome can be very different from one organism to another. One major difference is whether the organism is prokaryotic or eukaryotic. Prokaryotic genomes usually have little to no non-coding sequence, which means genes are packed closely together in operons along the chromosome. Eukaryotic genomes contain long stretches of non-coding DNA...

gene families

How Gene Families Evolve and Diversify

Gene families are groups of genes that are thought to come from a shared ancestor. They usually form when a gene is copied by mistake during cell division. The original gene stays under selection pressure to keep its job, while the extra copy can change more quickly over time. Some copied genes gain a new role in the organism. When that happens, they are called paralogs, which are two genes in the same species that evolved from one common ancestral gene. Gene families also include orthologs,...

types of genetic transfer between organisms

types-of-genetic-transfer-between-organisms

How Genes Move Within and Across Generations

Genetic transfer is the movement of genetic information from one organism to another. It happens in two main ways: vertical gene transfer and horizontal gene transfer. Vertical gene transfer moves genes from one generation to the next. It is much more common than horizontal gene transfer. Vertical gene transfer happens during both sexual reproduction and asexual reproduction. In both cases, one or more organisms pass some or all of their genome to their offspring. This kind of transfer occurs...

key terms and concepts

Learn how mutations change DNA through point mutations and frameshift mutations, and how these changes can affect genetic code, proteins, and traits.

How Mutations Change DNA | JoVE K12

molecular biology

JoVE Core 分子生物学通过清晰简洁的动画视频课程展示了细胞的分子过程。此外，在科学家在行动的视频中，这些概念的应用是通过现代实验室中的真实实验演示的。

new-jersey-student-learning-standards-for-science

New Jersey Student Learning Standards for Science

Life Science

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-1

Georgia Standards of Excellence

9-12

SB2.b

myJoVE Corporation

What is Meiosis?

Meiosis I

Meiosis is the division of a diploid cell into haploid cells forming sperm and eggs in animals through differentiation. Meiosis I is the first stage of ...

Meiosis II

Meiosis II entails cell division and segregation of the sister chromatids, resulting in the production of four unique haploid gametes. The steps for ...

Meiosis vs. Mitosis

Cell division is necessary for growth and reproduction in organisms. Mitosis aids cell growth and development by dividing somatic cells. In contrast, ...

Crossing over

Nondisjunction

Model chromosome progression through meiosis and fertilization in order to argue how the process of sexual reproduction leads to both genetic similarities and variation in diploid organisms. Compare and contrast the processes of sexual and asexual reproduction, identifying the advantages and disadvantages of each.
EXPLANATION: In 7.LS2.8, students develop an understanding that organisms grow from a single cell to a potentially complex multicellular organism through mitosis. It is critical to note that meiosis is introduced in 7.LS3.2 with the sole purpose to focus on the resulting daughter cells. Meiosis related content is categorized under LS3. While meiosis can be viewed as a unique form of cell division that provides a mechanism that results in offspring with a genotype unique unto itself. It should be recognized that mutations are the primary source of variation created through asexual reproduction by mitosis or binary fission and that mutations are passed to sexually reproduced offspring only when they are present in gametes. Attention should be drawn to the idea that population diversity must be advantageous considering the disadvantages of sexual reproduction (partner requirement and increased energy requirement). Meiosis and fertilization can be modeled with diagrams, 3D models, animations, etc. An emphasis should be placed on events that lead to genetic differences (mutations, crossing over, and random segregation) as well as events that generate similarities in parent and offspring (DNA replication and transmission). Similarities and differences in sexual and asexual reproductive strategies can be compiled and analyzed by students through the use of comparative models previously used (BIO1.LS1.5) and/or other resources (text, video, etc). These models may further be used to demonstrate how chromosomal-based diseases such as Trisomy 21 (Down syndrome) occur and/or how sterile hybrids, such as mules or seedless watermelons, cannot effectively complete meiosis due to non-homologous chromosomes from different parent species.

BIO1.LS3.1

Mutation, Gene Flow, and Genetic Drift

In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions ...

Gene Duplication and Divergence

The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of ...

Exon Recombination

The evolution of new genes is critical for speciation. Exon recombination, also known as exon shuffling or domain shuffling, is an important means of new ...

comparing-copy-number-variations-and-snps

Comparing Copy Number Variations and SNPs

Sequencing of the human genome has opened up several best-kept secrets of the genome. Scientists have identified thousands of genome variations that exist ...

Explain how protein formation results in phenotypic variation and discuss how changes in DNA can lead to somatic or germline mutations.
EXPLANATION: The general idea that genes create proteins and that these proteins determine the function and appearance of cells and organisms has been established in 7.LS3. In BIO1.LS1.4 the mechanism by which proteins are produced from genes is explored. This standard is designed to complete the connection between genotypes, protein synthesis, and resulting phenotypes by examining concrete examples. It should become clear that recessive traits occur when neither diploid copy of a gene produces a functional protein. Students could research the cause of specific and relatively simple examples of monogenic traits using a variety of level-appropriate resources (text, video, lecture, etc.) in order to elucidate the gene-protein-phenotype link. Classic examples could include but are not limited to: brown/blue base eye color due to melanin protein; PTC tasting due to a taste receptor on tongue cells; sickle cell anemia due to hemoglobin protein; PKU due to the enzyme that breaks down the amino acid phenylalanine; Hemophilia due to a clotting factor protein; ABO blood type due to an enzyme that attaches carbohydrates A, B, or nothing to the red blood cell. Students should recognize that phenotypic variation arises not only from genotypic variation, but also from gene expression variation, the latter of which can often be the result of environmental influences. For example: temperature regulates sex organ development in some fish species or fur color expression in some rabbit species; light regulates butterfly wing development; exercise increases muscle protein expression, isolation rearing in social animals alters brain gene expression; etc.

Pedigree Analysis

Overview

A pedigree is a diagram displaying a family&#x2019;s history of a trait. Analyzing pedigrees can reveal (1) whether a trait is dominant or ...

evolutionary-relationships-through-genome-comparisons

Evolutionary Relationships through Genome Comparisons

Genome comparison is one of the excellent ways to interpret the evolutionary relationships between organisms. The basic principle of genome comparison is ...

Phylogenetic Trees

Through pedigree analysis, identify patterns of trait inheritance to predict family member genotypes. Use mathematical thinking to predict the likelihood of various types of trait transmission.
EXPLANATION: In 7.LS3, students utilized Punnet squares to make predictions about allele combinations passed to offspring. Their predictions were limited to monohybrid crosses. While gene sequencing has permitted examination of the actual genetic information underlying a particular trait, that is a new process. Early models of investigating inheritance were dependent on pedigrees and the analysis of the appearance of phenotypes across generations. Modes of inheritance should include autosomal and sex-linked genes that are dominant/recessive, codominant, or incompletely dominant. Students can practice deductive reasoning using a basic set of criteria (including successive generation transmission and male/female ratio) in order to predict a mode of inheritance for a trait, define alleles for the trait, and assign genotypes to the family members of a given pedigree. Students can also practice using probability-based mathematics to predict offspring genotypes and phenotypes based on a given parental set.

BIO1.LS3.3

How Mutations Change DNA

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