In contrast to the complete synapsis in Trip13Gt/Gt pachytene spermatocytes (Figure 5A), in which SPO11 is available in leptonema to initiate (via DSB induction, Figure S2A and S2B) a recombination-driven homolog search, chromosome synapsis in doubly mutant spermatocytes was highly disrupted as in Spo11 single mutants (Figure 5B and 5C).