DNA repair
Molecular Biology · Genetics · Oncology
Say it: dee-en-AY rih-PAIR
DNA repair is the set of processes by which cells detect and correct damage and copying errors in their DNA, protecting the genome from mutation.
Also: DNA damage repair
Definition
What is DNA repair?
DNA repair is the collection of systems a cell uses to find and fix faults in its DNA. Damage is constant: ultraviolet light, chemicals such as those in tobacco smoke, reactive oxygen from the cell's own metabolism and plain chemical decay alter thousands of bases in every cell each day, and DNA polymerase sometimes adds the wrong nucleotide during replication. Faults left unrepaired can become permanent mutations.
Different pathways handle different problems. Proofreading by DNA polymerase removes most wrong bases as they are added, and mismatch repair fixes many it misses. Base excision repair removes single damaged bases, while nucleotide excision repair cuts out a short stretch around bulky lesions such as the thymine dimers caused by ultraviolet light; DNA polymerase fills the gap and DNA ligase seals it. Breaks through both strands are mended by homologous recombination, which copies the matching sequence from a sister chromatid, or by faster but less accurate non-homologous end joining.
Inherited defects in repair raise cancer risk: faulty mismatch repair causes Lynch syndrome, a hereditary form of colon cancer, faulty nucleotide excision repair causes xeroderma pigmentosum, and BRCA1 and BRCA2 mutations weaken recombination repair. Radiation and many chemotherapy drugs work by damaging DNA faster than tumor cells can fix it.
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Terms that go with it
- MutationA mutation is a lasting change in an organism's DNA sequence, ranging from a single altered base to large rearrangements of chromosomes.
- DNA polymeraseDNA polymerase is an enzyme that builds new DNA by adding nucleotides one at a time to a growing strand, using an existing strand as a template.
- DNA ligaseDNA ligase is an enzyme that links two pieces of DNA end to end, making a phosphodiester bond that seals a break in the sugar-phosphate backbone.
- CarcinogenA carcinogen is any substance, radiation, microbe or other exposure that can cause cancer or raise the chance of it developing.
- Tumor suppressor geneA tumor suppressor gene makes a protein that restrains cell division or repairs damage, so losing both working copies can help a cell turn cancerous.
- DNA replicationDNA replication is how a cell copies all of its DNA before it divides, so that each daughter cell receives a complete genome.
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Written for biofideX in plain words, after checking these references:
- OpenStax Biology 2e, 14.6 DNA Repair
- The Nobel Prize in Chemistry 2015: Press release
- NCBI MeSH: DNA Repair
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