In a species of fish, a black spot on the dorsal fin is observed in males and females. A fish breeder carries out a pair of reciprocal crosses and observes the following results.
Cross I Parents: black-spot male x nonspotted female
Progeny: 22 black-spot male
24 black-spot females
25 nonspotted males
21 nonspotted females
Cross II Parents: nonspotted male x black-spot female
Progeny: 45 black-spot males
53 nonspotted females
Identify which sex is heterogametic. Give genotypes for the parents in each cross, and explain the progeny proportions in each cross.
2. Mendel's Laws of Inheritance
Sex-Linked Genes