FIG. 6.

Interpretation of the observed meiotic phenotypes of rad50Δ and rad50S mutants. Both rad50Δ and rad50S mutants (at a restrictive temperature) are deficient for the removal of covalently bound Rec12^Spo11 after meiotic DSB formation, leading to low spore viability. However, a small fraction of cells are able to remove Rec12^Spo11 (through an unknown mechanism), allowing repair of the DSBs and viable spore formation. For the rad50Δ mutant, these survivors show a strong reduction in recombination rates, suggesting that they survive through a nonrecombinogenic survival mechanism. The rad50S cells are proficient for meiotic recombination (once Rec12^Spo11 has been removed), and the surviving spores therefore show normal meiotic recombination levels.