Fig. 5. Conditional knock-out of Sox9 in male and female germ cells. (A) Schematic diagram of breeding strategy. Although Sox9 was deleted in almost all oocytes of Sox9^flox/flox; Zp3:Cre females, Sox9 was deleted in only about half of the sperm of in Sox9^flox/flox; Prm:Cre males. Therefore, when Prm:Cre males and Zp3:Cre females were mated, Sox9^/ and Sox9^flox/ embryos were obtained at a 1:1 ratio (n=251). Only one Sox9^flox/flox embryo was obtained (0.4%). (B) PCR genotyping of Sox9 mutants obtained from the germ cell knock-out. No mosaicism was observed in homozygous Sox9 mutants. Sox9^flox, conditional (active) Sox9 allele; Sox9, recombined (inactive) Sox9 allele.