Practice question

Efficient homologous recombination depends on conversion of blunt double-strand breaks into 3' single-stranded overhangs suitable for Rad51 filament formation. MRX and Sae2 initiate this resection by Mre11 introducing endonucleolytic nick distal to 5' blocked ends such as Spo11 adducts or Ku-bound ends. Nick creation allows bidirectional exonucleolytic degradation, primarily 5'→3' by Exo1 or Sgs1-Dna2 in extended resection. This step commits cell to homology-directed repair because long 3' tails incompatible with NHEJ. Thus MRX does not perform strand invasion or direct ligation but provides substrate for homology search.