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

- [Istruttore] Le mutazioni puntiformi,

in cui un singolo
nucleotide viene modificato,

possono produrre una
proteina totalmente normale

o completamente non
funzionale, a seconda del tipo.

Questi includono mutazioni
silenti, missense,

nonsense e frameshift.

Le mutazioni silenti,
come suggerisce il nome,

non incidono sulla sequenza
aminoacidica della proteina.

Ad esempio, se il codone
CCA viene modificato in CCG,

continuerà a codificare per
la prolina dell'amminoacido

e la proteina funzionerà normalmente.

Le mutazioni missenso, d'altra parte,

comportano la sostituzione di
un amminoacido con un altro,

come l'arginina invece della prolina,

che può causare il
malfunzionamento della proteina.

Le mutazioni nonsense si verificano quando

si cambia un codone per un
amminoacido in uno di stop.

Ciò segnala alla cellula di
interrompere la traduzione,

risultante in una proteina
troncata prematuramente

che spesso non è funzionale.

Le mutazioni frameshift avvengono
se il riquadro di lettura,

raggruppati i gruppi di
tre nucleotidi in codoni,

viene spostato, spesso per
l'inserimento o la cancellazione

di uno o più nucleotidi.

Ciò si traduce in una
serie di nuovi codoni

che codificano per diversi aminoacidi,

creando una proteina anormale.

mutazioni

<h4>Panoramica</h4>

Le mutazioni sono cambiamenti nella sequenza del DNA. Questi cambiamenti possono verificarsi spontaneamente o possono essere indotti dall'esposizione a fattori ambientali. Le mutazioni possono essere caratterizzate in diversi modi: se e come alterano la sequenza di amminoacidi della proteina, se si verificano su una piccola o grande area del DNA e se si verificano nelle cellule somatiche o nelle cellule germinali.

<h4>Conseguenze delle mutazioni puntiformi a livello molecolare</h4>

Le mutazioni che si verificano in un singolo nucleotide sono chiamate mutazioni puntiformi. Quando le mutazioni puntiformi si verificano all'interno dei geni, le conseguenze possono variare in termini di gravità a seconda di ciò che accade alla sequenza di amminoacidi codificati. Una mutazione silenziosa non cambia l'identità dell'amminoacido e non avrà alcun effetto su un organismo. Una mutazione errata modifica un singolo aminoacido e gli effetti potrebbero essere gravi se il cambiamento altera la funzione della proteina. Una mutazione senza senso produce un codone di arresto che tronca la proteina, probabilmente rendendola non funzionale. Le mutazioni del frameshift si verificano quando uno o più nucleotidi vengono inseriti o eliminati da una sequenza di DNA codificante di proteine, che interessano tutti i codoni a valle della posizione della mutazione.

<h4>Le alterazioni cromosomiche sono mutazioni su larga scala</h4>

Il tipo più drastico di mutazione, l'alterazione cromosomica, cambia la struttura fisica di un cromosoma. Le alterazioni cromosomiche possono includere la cancellazione, la duplicazione o l'inversione di grandi distese di DNA all'interno di un singolo cromosoma o l'integrazione di una porzione di un cromosoma diverso. Queste mutazioni sono in genere molto più gravi delle mutazioni puntiformi perché comprendono molti geni ed elementi regolatori. Le alterazioni cromosomiche possono essere rilevate cariotipizzando la cellula interessata.

<h4>Solo le mutazioni germinali sono ereditate</h4>

Le mutazioni possono verificarsi in qualsiasi cellula, ma solo le mutazioni germinali (quelle presenti negli ovuli e negli spermatozoi) possono essere trasmesse alla prole. Ad esempio, le malattie ereditarie sono un sottotipo di malattia genetica causata da mutazioni germinali deleterie. Possono essere autosomici, che si verificano sui cromosomi da uno a 22, o legati al sesso, che si verificano sul cromosoma X o Y. Un esempio di malattia ereditaria è la fibrosi cistica (CF), una malattia che colpisce principalmente i polmoni. È causato da una delezione all'interno del CFTR genico che rimuove un singolo aminoacido dalla proteina CFTR. La CF è una malattia recessiva autosomica, il che significa che una persona con una copia mutata del gene e una copia normale non svilupperà la malattia; altre malattie, come la Malattia di Huntington, un disturbo neurodegenerativo, sono autosomiche dominanti, il che significa che solo una copia mutata del gene è necessaria per lo sviluppo della malattia.

<h4>Alcune mutazioni sono causate da fattori ambientali</h4>

Entrambe le mutazioni somatiche, quelle che si verificano al di fuori della germinale, e le mutazioni germinali possono sorgere spontaneamente durante la replicazione del DNA, ma possono anche essere causate dall'esposizione a radiazioni o sostanze chimiche nell'ambiente. I fattori esterni che danneggiano il DNA e causano mutazioni sono chiamati mutageni. Un mutageno ambientale ben caratterizzato è la radiazione ultravioletta (UV). La radiazione UV trasporta più energia della luce visibile e danneggia il DNA rompendo i legami tra le coppie di basi, facendo sì che le basi della timina sullo stesso filamento di DNA si accoppiano l'una con l'altra nei caratteristici dimeri della timina. Il sole è una fonte naturale di radiazioni UV. Le lunghezze d'onda più dannose, UV-C, sono intercettate in alto nell'atmosfera, ma i raggi UV-A e UV-B raggiungono la superficie della Terra. Le fonti artificiali di esposizione ai raggi UV includono letti abbronzanti, che trasmettono principalmente raggi UV-A con piccole quantità di UV-B. Fortunatamente, le cellule hanno meccanismi per riparare il DNA danneggiato, ma a volte il danno non viene riparato prima della divisione cellulare in cellule che si dividono rapidamente, come le cellule della pelle. Se il danno al DNA si verifica in una regione genomica importante per la regolazione della crescita cellulare e della divisione, può portare al cancro se non viene riparato.

Mutazioni

Overview

Mutations are changes in the sequence of DNA. These changes can occur spontaneously or they can be induced by exposure to environmental factors. ...

Education

Didattica

JoVE Core

Molecular Biology

Biologia Molecolare

Unit 1

Unità 1

DNA, Cells, and Evolution

DNA, cellule ed evoluzione

KEY TERMS AND CONCEPTS

TERMINI E CONCETTI CHIAVE

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

Le video animazioni di JoVE Core Molecular Biology, organizzate in video lezioni, illustrano i processi molecolari cellulari in maniera chiara e concisa. Inoltre, nei video di "scienziati in azione", i concetti scientifici vengono applicati e dimostrati da ricercatori attraverso esperimenti in laboratorio.

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

Description

Transcript

Tags

More videos by Standards