Male Sex Reversal in Gynogenetic XX Females of Common Carp (Cyprinus carpio L.) by a Recessive Mutation in a Sex-Determining Gene

The genetic analysis of a mutation that produces male sex reversal in gynogenetic female common carp, Cyprinus carpio L., is described. The inheritance of this mutation, termed masculinization (mas)-1, is unequivocally recessive. Crossing of homozygous XX; mas-1/ mas-1 males with heterozygous XX; mas-1/mas+ females produces equal ratios of female and male plus intersex offspring. The occurrence of a few males or intersexes in XX; mas+ / mas-1 F, hybrid progeny shows that some mas+ / mas-1 animals undergo sex reversal under unfavorable conditions. The possibility that the mas mutant represents an autosomal sex-determining gene that induces precocious male development in XX females is discussed.