Homologous recombination is the primary high-fidelity mechanism for repairing DNA double-strand breaks in the S and G2 phases of the cell cycle. Which protein coats the single-stranded DNA overhangs and catalyzes strand invasion into the homologous duplex?

• A Ku70/Ku80 heterodimer
• B Rad51 ✓
• C BRCA1
• D DNA-PKcs

Explanation

Rad51 is the eukaryotic recombinase that assembles into nucleoprotein filaments on 3' single-stranded DNA overhangs and catalyzes homology search and strand invasion into the intact sister chromatid. Ku70/Ku80 and DNA-PKcs are components of the non-homologous end joining (NHEJ) pathway, which is error-prone and active throughout the cell cycle. BRCA1 facilitates homologous recombination but does not directly perform strand invasion.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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