Summary
Mechanisms such as mismatch, excision and double-strand break repair that fix errors and damage in DNA.
In depth
Proofreading corrects errors during replication. Mismatch repair fixes those that remain. Base excision repair removes damaged bases (glycosylase), nucleotide excision repair removes bulky lesions such as UV pyrimidine dimers, and double-strand breaks are repaired by homologous recombination or end joining.
Defects cause disease: xeroderma pigmentosum (excision repair) gives UV sensitivity and skin cancer; BRCA mutations impair recombination.
Cells face about 10,000 to 100,000 lesions per cell per day. Direct reversal enzymes such as MGMT remove methyl groups, photolyase uses light to fix UV dimers in many organisms (but not placental mammals), and double-strand breaks are fixed by homologous recombination or end joining. Mismatch repair recognises the new strand by nicks and fixes replication errors.
Defects cause disease: xeroderma pigmentosum (nucleotide excision repair) leads to extreme UV sensitivity and skin cancer, Lynch syndrome (mismatch repair) to colon cancer, and BRCA1/2 defects (recombination) to breast and ovarian cancer. PARP inhibitors exploit this by killing BRCA-deficient cells.
Key idea: repair pathways are specialised and overlapping, giving cells a robust defence against damage.
Frequently asked questions
What is DNA Repair?
Mechanisms such as mismatch, excision and double-strand break repair that fix errors and damage in DNA.
Which area of biology covers DNA Repair, and how advanced is it?
DNA Repair is one of the 52 topics in Molecular Biology. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Homologous Recombination, Mutation and Repair Link, Non-Homologous End Joining.
Can you give an example of DNA Repair?
Lynch syndrome is caused by mismatch repair gene defects.
What should I learn before DNA Repair?
Work through the Beginner topics in Molecular Biology first, such as Central Dogma, DNA Replication, Base Pairing, then return to DNA Repair. Intermediate topics assume the Beginner vocabulary.
What topics are related to DNA Repair?
The closest topics to DNA Repair are Homologous Recombination, Mutation and Repair Link, Non-Homologous End Joining, DNA Methylation. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand DNA Repair?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for DNA Repair. To practise the whole of Molecular Biology, use the Molecular Biology quiz.
How is DNA Repair different from Homologous Recombination?
DNA Repair: Mechanisms such as mismatch, excision and double-strand break repair that fix errors and damage in DNA. Homologous Recombination: An accurate repair pathway and meiotic mechanism exchanging DNA between similar sequences using RAD51. Read both side by side and note what each one explains.
How should I study DNA Repair step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Homologous Recombination and explain the difference aloud. Finally, take the Molecular Biology quiz and come back to this page for any question you miss.