Name: dna damage repair by excision
Uploaded: 2026-08-26T08:19:31.026Z
Duration: 1 min 46 s
Channel: JoVE

K12 Standards

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

New Jersey Student Learning Standards for Science

High School

Life Science

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

From Molecules to Organisms: Structures and Processes

HS-LS1-1

Nucleotide Excision Repair

A exposi&#xE7;&#xE3;o do DNA &#xE0; luz ultravioleta e certos carcin&#xF3;genos qu&#xED;micos pode causar uma les&#xE3;o volumosa, uma distor&#xE7;&#xE3;o espec&#xED;fica de sua estrutura normal. Este tipo de dano pode ser corrigido por um processo chamado reparo por excis&#xE3;o de nucleot&#xED;deos. O processo come&#xE7;a quando um complexo enzim&#xE1;tico mostrado aqui em E.Coli, contendo as prote&#xED;nas UvrA e UvrB viaja ao longo do DNA e deteta a aberra&#xE7;&#xE3;o f&#xED;sica da les&#xE3;o.Nesse local, as fitas s&#xE3;o separadas, e enzimas endonuclease, como a UvrC, clivam a fita em ambos os lados do dano. A enzima DNA helicase, em seguida, remove a pe&#xE7;a cortada. Outra enzima, a DNA polimerase preenche a lacuna com novos nucleot&#xED;deos.Finalmente, a enzima DNA ligase sela as bordas entre o DNA novo e o velho, completando o reparo.

Schärer, Orlando D. "Reparo por excisão de nucleotídeos em eucariotos". Perspectivas de Cold Spring Harbor em biologia 5, nº 10 (2013): a012609. [<a href="https://dx.doi.org/10.1101%2Fcshperspect.a012609">Fonte</a>]

reparação da excisão de nucleótidos

<h4>Vis&#xE3;o Geral</h4>
 
 A exposi&#xE7;&#xE3;o a mutag&#xE9;nios pode danificar o DNA e resultar em les&#xF5;es volumosas que distorcem a estrutura de dupla h&#xE9;lice ou impedem a transcri&#xE7;&#xE3;o adequada. O DNA danificado pode ser detectado e reparado em um processo chamado repara&#xE7;&#xE3;o da excis&#xE3;o de nucle&#xF3;tidos (NER). A NER emprega um conjunto de prote&#xED;nas especializadas que primeiro inspeccionam o DNA para detectar uma regi&#xE3;o danificada. Em seguida, as prote&#xED;nas da NER separam as cadeias e removem a &#xE1;rea danificada. Por fim, elas coordenam a substitui&#xE7;&#xE3;o por novos nucle&#xF3;tidos correspondentes.
 
 <h4>Distor&#xE7;&#xE3;o e dano do DNA</h4>
 
 As c&#xE9;lulas s&#xE3;o regularmente expostas a mutag&#xE9;nios&#x2014;fatores no ambiente que podem danificar o DNA e gerar muta&#xE7;&#xF5;es. A radia&#xE7;&#xE3;o UV &#xE9; uma das muta&#xE7;&#xF5;es mais comuns e estima-se que introduza um n&#xFA;mero significativo de altera&#xE7;&#xF5;es no DNA. Estas incluem dobras ou tor&#xE7;&#xF5;es na estrutura que podem bloquear a replica&#xE7;&#xE3;o ou transcri&#xE7;&#xE3;o do DNA. Se esses erros n&#xE3;o forem corrigidos, o dano pode causar muta&#xE7;&#xF5;es que, por sua vez, podem resultar em cancro ou doen&#xE7;a, dependendo das sequ&#xEA;ncias que s&#xE3;o interrompidas.
 
 <h4>Identifica&#xE7;&#xE3;o e repara&#xE7;&#xE3;o de regi&#xF5;es danificadas</h4>
 
 A repara&#xE7;&#xE3;o da excis&#xE3;o de nucle&#xF3;tidos conta com complexos proteicos espec&#xED;ficos para reconhecer regi&#xF5;es danificadas do DNA e marc&#xE1;-las para remo&#xE7;&#xE3;o e repara&#xE7;&#xE3;o. Em procariotas, o processo envolve tr&#xEA;s prote&#xED;nas&#x2014;UvrA, UvrB e UvrC. As duas primeiras prote&#xED;nas trabalham juntas como um complexo, viajando ao longo das cadeias de DNA para detectar quaisquer aberra&#xE7;&#xF5;es f&#xED;sicas.
 
 Uma vez identificadas, as cadeias s&#xE3;o separadas no local danificado, e enzimas endonuclease, como UvrC, cortam e removem a regi&#xE3;o afetada. A DNA polimerase preenche a lacuna com novos nucle&#xF3;tidos, e a enzima DNA ligase sela ent&#xE3;o as extremidades do DNA novo com o antigo.
 
 <h4>Muta&#xE7;&#xF5;es na NER t&#xEA;m graves consequ&#xEA;ncias</h4>
 
 Em procariotas, o complexo NER consiste nas tr&#xEA;s prote&#xED;nas Uvr, mas em eucariotas, mais de uma d&#xFA;zia de prote&#xED;nas trabalham para regular a repara&#xE7;&#xE3;o do DNA. Em humanos, muta&#xE7;&#xF5;es na via NER podem causar doen&#xE7;as como xerodermia pigmentosa (XP), que est&#xE1; associada a um aumento de 2000 vezes da incid&#xEA;ncia de cancro da pele. Indiv&#xED;duos que sofrem de XP s&#xE3;o altamente sens&#xED;veis &#xE0; exposi&#xE7;&#xE3;o UV e podem desenvolver queimaduras graves na pele ap&#xF3;s apenas alguns minutos de exposi&#xE7;&#xE3;o &#xE0; luz solar. Al&#xE9;m disso, os pacientes com XP podem apresentar sinais de envelhecimento precoce e, muitas vezes, desenvolver anormalidades neurol&#xF3;gicas. Sem um mecanismo de repara&#xE7;&#xE3;o a funcionar corretamente, os danos no DNA podem acumular-se e levar a morte celular anormal ou a tumores potencialmente cancer&#xED;genos.

Reparação da Excisão de Nucleótidos

Overview

Exposure to mutagens can damage DNA and result in bulky lesions that distort the double-helix structure or impede proper transcription. Damaged ...

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Education

JoVE Core

Biology

Biologia

Genetics

Genética

DNA Structure and Function

Estrutura e Função do DNA

KEY TERMS AND CONCEPTS

TERMOS-CHAVE E CONCEITOS

dna damage repair by excision

DNA damage repair by excision protects cells from mutagens that can change DNA. Exposure to environmental mutagens can create bulky lesions that bend the double helix or block transcription. If these changes are not repaired, they can lead to mutations and may contribute to cancer or disease, depending on which DNA sequences are affected.

Nucleotide excision repair, or NER, is the process that detects and removes this kind of damage. Specialized proteins scan the DNA for a damaged region, then separate the strands around it. The damaged section is cut out, and a matching stretch of new nucleotides is added in its place.

UV radiation is one of the most common mutagens and can introduce many DNA changes. These changes can cause kinks in the DNA structure and interfere with replication or transcription. Because of this, cells rely on repair systems to keep damaged DNA from building up.

In prokaryotes, NER uses three main proteins: UvrA, UvrB, and UvrC. UvrA and UvrB work together as a complex and move along the DNA to spot physical damage. After the damaged site is found, the strands are separated, UvrC cuts out the affected section, DNA polymerase fills the gap, and DNA ligase seals the remaining break.

NER is more complex in eukaryotes, where more than a dozen proteins help control DNA repair. In humans, mutations in the NER pathway can cause xeroderma pigmentosum, or XP. This disorder is linked to a 2000-fold increase in skin cancer risk, strong sensitivity to UV light, severe burns after only a few minutes in sunlight, premature aging, and neurological problems. Without a working repair system, DNA damage can accumulate and lead to abnormal cell death or cancerous tumors.

DNA Damage Repair by Excision

the dna helix

How DNA Stores Genetic Information

DNA stores genetic information that is passed from one generation to the next in organisms and most viruses. It is built from two strands of nucleotides that twist together into a double helix. The story of how scientists uncovered this structure developed step by step over nearly a century. Each DNA strand is made of nucleotides. A nucleotide contains the sugar deoxyribose, a phosphate group, and one of four nitrogen bases: adenine (A), guanine (G), cytosine (C), or thymine (T). Adenine and...

dna packaging

Chromatin and Histones in DNA Packing

Eukaryotic cells must pack long DNA molecules into the nucleus, and chromatin makes that possible. DNA wraps around proteins called histones to form nucleosomes, which are the main unit of DNA packaging. Nucleosomes then coil into compact chromatin fibers. The amount of DNA in a cell is much larger than it first seems. A single human skin cell has about 3 billion base pairs of DNA, and if that DNA were stretched out in a line, it would be about 2 meters long. With about 50 trillion cells in...

organization of genes

Genes, Introns, and Regulatory DNA

Eukaryotic genes are arranged within DNA along with non-coding regions that help control gene activity. A DNA strand includes genes and intergenic regions, which are the stretches between genes. These regions do not code for proteins, but they can contain important regulatory elements such as promoters, enhancers, and silencers. A gene itself is not a single continuous coding block. It usually contains protein-coding exons and non-coding introns. After DNA is transcribed into pre-mRNA in the...

karyotyping

Chromosome Stains for Detecting Disorders

Chromosome staining helps scientists find genetic disorders by showing the number and physical features of chromosomes. These features appear after DNA condenses into chromosomes during mitosis. Cytogeneticists then stop mitosis and stain the chromosomes to study their banding pattern. The pattern reveals details such as chromosome number, shape, and type. A chromosome description like this is called a karyotype. To create one, scientists take an image of the stained chromosomes and identify...

replication in prokaryotes

How Prokaryotic DNA Is Copied

Prokaryotic DNA is copied through a coordinated process with three main stages: initiation, elongation, and termination. It begins when initiator proteins bind to the single origin of replication, or ori, on the cell’s circular chromosome. The DNA then copies around the circle in both directions, starting from two replication forks, and this produces two DNA molecules. Several proteins work together to open and protect the DNA during replication. Topoisomerase cuts one side of the...

replication in eukaryotes

Eukaryotic DNA Copying and Telomeres

Eukaryotic DNA copying is tightly regulated and must duplicate many linear chromosomes before cell division. The process is highly conserved and uses many proteins with specialized roles. It moves through initiation, elongation, and termination, and it ends with two complete sets of chromosomes in the nucleus. Eukaryotic replication shares basic steps with prokaryotic DNA replication, but the larger genome and linear chromosomes require more proteins. Replication begins at multiple origins of...

proofreading

DNA Polymerase Fixes Replication Errors

DNA polymerase helps copy DNA and fix mistakes during replication. It adds nucleotides in a sequence that matches the template DNA strand. The enzyme also has a higher affinity for the correct base, which helps keep DNA replication accurate. As new genomic DNA is made, it is synthesized in the 5’ to 3’ direction. In many cells, DNA polymerases have different jobs in this process. DNA polymerase delta and DNA polymerase epsilon can proofread when nuclear DNA is being copied. These polymerases...

mismatch repair

DNA Mismatch Repair in Replication

DNA mismatch repair fixes copying errors that happen during DNA replication. When DNA polymerase makes a mistake, the cell can detect a wrong base pair, such as A with G or T with C, and replace it with the correct nucleotide. This repair system works in both prokaryotes and eukaryotes and depends on several proteins. The Mutator protein family plays a central role in this process. In bacteria such as Escherichia coli, MutS first binds the mismatch. MutL then helps identify which strand is the...

nucleotide excision repair

DNA damage repair by excision protects cells from mutagens that can change DNA. Exposure to environmental mutagens can create bulky lesions that bend the double helix or block transcription. If these changes are not repaired, they can lead to mutations and may contribute to cancer or disease, depending on which DNA sequences are affected. Nucleotide excision repair, or NER, is the process that detects and removes this kind of damage. Specialized proteins scan the DNA for a damaged region, then...

mutations

DNA Changes From Point Mutations to UV Damage

Mutations are changes in the DNA sequence. They can happen by chance during DNA copying, or they can be caused by environmental factors such as radiation and chemicals. Scientists also describe mutations by how much DNA they affect, how they change a protein, and whether they happen in body cells or germline cells. Some mutations affect only one nucleotide, which is a point mutation. When a point mutation falls inside a gene, the outcome depends on how the amino acid sequence changes. A silent...

transcription

Transcription and Gene Control

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translation

Protein Synthesis and mRNA Decoding

Protein synthesis begins when ribosomes decode messenger RNA (mRNA) and build a chain of amino acids. This final step of gene expression is called translation. The finished chain is a polypeptide, which can later become a functional protein. Proteins are often called the building blocks of life because they make up much of the body, from muscle fibers to hairs and immune system parts. The instructions for each protein are encoded in genes found in the DNA of every cell. In biology, the central...

bacterial transformation

Griffith’s Mouse Experiment and DNA

Bacterial transformation explains how DNA can move into bacteria and change their traits. Frederick Griffith first noticed this in 1928 while studying pneumonia-causing Streptococcus pneumoniae in mice. He compared one pathogenic strain with one non-pathogenic strain and found that only the pathogenic strain killed the host mice. Griffith made an unexpected discovery when he killed the pathogenic bacteria and mixed their remains with live, non-pathogenic bacteria. The mixture killed the mice,...

key terms and concepts

Learn how nucleotide excision repair fixes UV-induced DNA damage by cutting out lesions and replacing them with new DNA. Includes prokaryotes, humans, and XP.

DNA Damage Repair by Excision | JoVE K12

JoVE Core series brings biology to life through over 300 concise and easy-to-understand animated video lessons that explain key concepts in biology, plus more than 150 scientist-in-action videos that show actual research experiments conducted in today’s laboratories.

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A coleção JoVE Core dá vida à biologia através de mais de 300 vídeos de animação concisos e fáceis de entender que explicam conceitos-chave de biologia, além de mais de 150 vídeos de Cientistas em ação que mostram experimentos reais em pesquisa realizados nos laboratórios atualmente.

Next Generation Science Standards

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-2

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-1.

The DNA Helix

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 ...

Organization of Genes

Overview

The genomes of eukaryotes can be structured in several functional categories. A strand of DNA is comprised of genes and intergenic regions. ...

Karyotyping

Describing the number and physical features of chromosomes can reveal abnormalities that underlie genetic diseases. This description is facilitated by ...

Replication in Prokaryotes

Overview

DNA replication has three main steps: initiation, elongation, and termination. Replication in prokaryotes begins when initiator proteins bind to ...

Replication in Eukaryotes

Overview

In eukaryotic cells, DNA replication is highly conserved and tightly regulated. Multiple linear chromosomes must be duplicated with high ...

Proofreading

Synthesis of new DNA molecules starts when DNA polymerase links nucleotides together in a sequence that is complementary to the template DNA strand. DNA ...

Mismatch Repair

Overview

Organisms are capable of detecting and fixing nucleotide mismatches that occur during DNA replication. This sophisticated process requires ...

Mutations

Overview

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

Transcription

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

Translation

Lesson: Translation
Translation is the process of synthesizing proteins from the genetic information carried by messenger RNA (mRNA). Following ...

Bacterial Transformation

In 1928, bacteriologist Frederick Griffith worked on a vaccine for pneumonia, which is caused by Streptococcus pneumoniae bacteria. Griffith studied two ...

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.

Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.

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structural-organization-of-the-human-body-an-overview

Structural Organization of the Human Body: An Overview

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Functions of Life

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Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

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Assessment Boundary: Assessment does not include interactions and functions at the molecular or chemical reaction level.

HS-LS1-2

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Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

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Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.

HS-LS1-3

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Inhibition of CDK Activity

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Chromosome Duplication

Cohesins

Condensins

The Mitotic Spindle

Centrosome Duplication

Spindle Assembly

Attachment of Sister Chromatids

Forces Acting on Chromosomes

Separation of Sister Chromatids

Live Cell Imaging of Mitosis

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The Spindle Assembly Checkpoint

Cell Division

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Anaphase A and B

Anaphase Promoting Complex

The Contractile Ring

Determining the Plane of Cell Division

The Phragmoplast

Distribution of Cytoplasmic Content

An Introduction to Cell Division

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Cell Cycle Analysis

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Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.

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HS-LS1-4

Photosynthesis

Autotrophs

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Photosystems

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The Photochemical Reaction Center

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The Antenna Complex

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the-z-scheme-of-electron-transport-in-photosynthesis

The Z-Scheme of Electron Transport in Photosynthesis

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The Calvin Benson Cycle

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Use a model to illustrate how photosynthesis transforms light energy into stored chemical energy.

Clarification statement: Emphasis is on illustrating inputs and outputs of matter and the transfer and transformation of energy in photosynthesis by plants and other photosynthesizing organisms. Examples of models could include diagrams, chemical equations, and conceptual models.

Assessment Boundary: Assessment does not include specific biochemical steps.

HS-LS1-5

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lipid-derived-compounds-in-the-human-body

Lipid-derived Compounds in the Human Body

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Fats as Energy Storage Molecules

What are Proteins?

Protein Organization

Globular Proteins

In organisms, proteins are the most abundant macromolecules. They act as the building blocks of life and play various crucial roles in the body. Proteins ...

Construct and revise an explanation based on evidence for how carbon, hydrogen, and oxygen from sugar molecules may combine with other elements to form amino acids and/or other large carbon- based molecules.

Clarification statement: Emphasis is on using evidence from models and simulations to support explanations.

Assessment Boundary: Assessment does not include the details of the specific chemical reactions or identification of macromolecules.

HS-LS1-6

DNA Damage Repair by Excision

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