Practice question

Homology search by RecA family does not require long perfect match for initial pairing, but minimal stretch of stable base pairing is necessary to maintain joint molecule. Biophysical single-molecule studies reveal that invasion requires approximately 8 base-pair microhomology for initiation, while stable D-loop that resists helicase rejection requires roughly 15 base-pair contiguous homology sampled in triplets. Below threshold, heteroduplex dissociates rapidly. This requirement prevents promiscuous recombination between short repeats causing deletions, while permitting efficient pairing between sister chromatids or homologs sharing genome-wide homology, ensuring fidelity and suppressing ectopic recombination.