Investigation of fertility phenotypes of Dmc1 hybrid founder mice. (A) Representative immunofluorescence staining of DMC1 (red) in testis nuclear spreads from two founder mice, one with DMC1 present (Dmc1^+/+) and with DMC1 ablated (Dmc1^−/−) with costaining of the synaptonemal complex protein SYCP3, which labels the chromosome axis (green) in zygotene (top panels) and pachytene/pseudo-pachytene (middle panels). Lower panels show pachytene/pseudo-pachytene stage staining of SYCP1 (red), labeling the synaptonemal-complex transverse filament, and SYCP3 (green) staining of the chromosome axes. Pronounced asynapsis is visible in a founder with ablated DMC1 (Dmc1^−/−). (B,C) Fertility parameters for the founder mice showing complete ablation of DMC1 (Dmc1^−/−; n = 7) with age-matched wild-type B6CASTF1 mice (Dmc1^+/+; n = 10), with normalized testis weight (B) and total caudal sperm count (C).