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

- [Instructeur] Blootstelling van DNA aan ultraviolet licht en bepaalde chemische carcinogenen kan een volumineuze laesie veroorzaken, een specifieke vervorming van zijn normale structuur.
 Dit soort beschadiging kan gerepareerd worden door een proces dat nucleotide excisie-reparatie heet.
 Het proces begint wanneer een enzymcomplex hier getoond in E.
Coli, dat de prote&#xEF;nen UvrA en UvrB bevat, zich door het DNA verplaatst en de fysieke afwijking van de laesie detecteert.
 Op die locatie zijn de strengen gescheiden en endonuclease enzymen, zoals UvrC, splitsen de streng aan beide zijden van de schade.
 De enzym DNA-helicase verwijdert dan het afgesneden stuk.
Een ander enzym DNA-polymerase vult de opening met nieuwe nucleotiden.
 Tenslotte sluit het enzym DNA-ligase de randen tussen het nieuwe en oude DNA af en voltooid zo de herstelling.

reparatie van nucleotide-excisie

<h4>Overzicht</h4>

Blootstelling aan mutagenen kan DNA beschadigen en resulteren in omvangrijke laesies die de dubbele helixstructuur verstoren of een goede transcriptie belemmeren. Beschadigd DNA kan worden gedetecteerd en gerepareerd in een proces dat nucleotide-excisieherstel (NER) wordt genoemd. NER maakt gebruik van een reeks gespecialiseerde eiwitten die eerst DNA scannen om een beschadigd gebied te detecteren. Vervolgens scheiden NER-eiwitten de strengen en snijden het beschadigde gebied weg. Ten slotte co&#xF6;rdineren ze de vervanging door nieuwe, bijpassende nucleotiden.

<h4>DNA-vervorming en schade</h4>

Cellen worden regelmatig blootgesteld aan mutagene stoffen &#x2013; factoren in de omgeving die het DNA kunnen beschadigen en mutaties kunnen genereren. UV-straling is een van de meest voorkomende mutagenen en brengt naar schatting een aanzienlijk aantal veranderingen in het DNA teweeg. Deze omvatten bochten of knikken in de structuur die DNA-replicatie of transcriptie kunnen blokkeren. Als deze fouten niet worden verholpen, kan de schade mutaties veroorzaken die op hun beurt kunnen resulteren in kanker of ziekten, afhankelijk van welke sequenties worden verstoord.

<h4>Identificatie en reparatie van beschadigde gebieden</h4>

Reparatie van nucleotide-excisie is afhankelijk van specifieke eiwitcomplexen om beschadigde DNA-gebieden te herkennen en deze te markeren voor verwijdering en reparatie. Bij prokaryoten zijn bij het proces drie eiwitten betrokken: UvrA, UvrB en UvrC. De eerste twee eiwitten werken samen als een complex en reizen langs de DNA-strengen om eventuele fysieke afwijkingen te detecteren.

Eenmaal ge&#xEF;dentificeerd, worden de strengen op de beschadigde locatie gescheiden, en endonuclease-enzymen zoals UvrC knippen het getroffen gebied door en snijden het uit. DNA-polymerase vult het gat met nieuwe nucleotiden, en vervolgens sluit het DNA-ligase-enzym de randen tussen het nieuwe en oude DNA af.

<h4>Mutaties in NER hebben ernstige gevolgen</h4>

Bij prokaryoten bestaat het NER-complex uit de drie Uvr-eiwitten, maar bij eukaryoten zijn meer dan een dozijn eiwitten werkzaam om DNA-reparatie te reguleren. Bij mensen kunnen mutaties in de NER-route ziekten veroorzaken zoals xeroderma pigmentosum (XP), wat gepaard gaat met een 2000-voudige toename van de incidentie van huidkanker. Mensen die lijden aan XP zijn zeer gevoelig voor blootstelling aan UV-straling en kunnen na slechts enkele minuten blootstelling aan zonlicht ernstige brandwonden ontwikkelen. Bovendien kunnen XP-pati&#xEB;nten tekenen van vroegtijdige veroudering vertonen en vaak neurologische afwijkingen ontwikkelen. Zonder een goed werkend reparatiemechanisme kan DNA-schade zich ophopen en leiden tot abnormale celdood of mogelijk kankertumoren.

Reparatie van nucleotide-excisie

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

Biologie

Genetics

Genetica

DNA Structure and Function

DNA-structuur en -functie

KEY TERMS AND CONCEPTS

BELANGRIJKE TERMEN EN CONCEPTEN

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

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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

Transcription and gene control explain how cells make RNA from DNA and decide which genes are active. RNA polymerase copies a DNA sequence into RNA, and this is the first step in making a protein from a gene. Many other proteins and control sequences help make messenger RNA, or mRNA, correctly. In eukaryotes, the DNA is first copied into a primary RNA, also called pre-mRNA. This RNA can then be processed into mature mRNA, which serves as the template for protein synthesis. In prokaryotes such...

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

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biology

Next Generation Science Standards

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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. ...

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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 ...

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Lesson: Translation
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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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