Summary
An accurate repair pathway and meiotic mechanism exchanging DNA between similar sequences using RAD51.
In depth
After a double-strand break, ends are resected, RAD51 forms a filament that finds a matching sequence in the sister chromatid or homologue, and DNA is synthesised using it as a template. In meiosis, Spo11 makes deliberate breaks.
It is error-free when the sister chromatid is used.
HR is accurate since it uses an intact homologous template. It is active in S and G2 phases when sister chromatids are available. Steps are resection by MRN and CtIP, loading of RPA and then RAD51 (assisted by BRCA2), strand invasion forming a D-loop, DNA synthesis, and resolution through Holliday junctions or dissolution.
The same machinery makes meiotic crossovers (using DMC1) and helps restart stalled replication forks. In gene targeting, researchers exploit HR to insert changes, as in knockout mice (Nobel Prize 2007, Capecchi, Evans and Smithies). Defects cause cancer predisposition.
Key idea: HR copies information from a template, so it restores the original sequence, unlike end joining.
Frequently asked questions
What is Homologous Recombination?
An accurate repair pathway and meiotic mechanism exchanging DNA between similar sequences using RAD51.
Which area of biology covers Homologous Recombination, and how advanced is it?
Homologous Recombination is one of the 52 topics in Molecular Biology. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include DNA Repair, CRISPR-Cas9 Mechanism, DNA Replication.
Can you give an example of Homologous Recombination?
BRCA2 loads RAD51, so BRCA2 mutations impair repair and PARP inhibitors exploit this.
What should I learn before Homologous Recombination?
Work through the Beginner topics in Molecular Biology first, such as Central Dogma, DNA Replication, Base Pairing, then return to Homologous Recombination. Advanced topics assume the Intermediate vocabulary.
What topics are related to Homologous Recombination?
The closest topics to Homologous Recombination are DNA Repair, CRISPR-Cas9 Mechanism, DNA Replication, Non-Homologous End Joining. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Homologous Recombination?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Homologous Recombination. To practise the whole of Molecular Biology, use the Molecular Biology quiz.
How is Homologous Recombination different from DNA Repair?
Homologous Recombination: An accurate repair pathway and meiotic mechanism exchanging DNA between similar sequences using RAD51. DNA Repair: Mechanisms such as mismatch, excision and double-strand break repair that fix errors and damage in DNA. Read both side by side and note what each one explains.
How should I study Homologous Recombination 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 DNA Repair and explain the difference aloud. Finally, take the Molecular Biology quiz and come back to this page for any question you miss.