Question

In chickens, males have two Z sex chromosomes (ZZ) and females have one Z and one W sex chromosome (ZW). The mechanism for inheritance of the sex chromosomes is exactly the same as for X and Y sex chromosomes in other species. In chickens, the character of "barred" or striped feathers is Zchromosome linked. The barred feather allele ZB is dominant to the nonbarred feather allele Zb. Write down the genotype that would result in a nonbarred male and a barred female and explain why these are the only genotypes that could result in these phenotypes.

Answer 1

A nonbarred male chicken would have the genotype ZbZb and a barred female would have the genotype ZBZW, as the dominant ZB allele on the Z chromosome causes the barred phenotype in chickens.

Step-by-step explanation:

In chickens, the genotype that would result in a nonbarred male would be ZbZb, as males have two Z chromosomes and for a male to express the recessive nonbarred phenotype, both Z chromosomes must carry the recessive allele.

Conversely, the genotype for a barred female would be ZBZW, since females are ZW and the presence of a single dominant ZB allele on the Z chromosome is enough to express the barred phenotype. It is important to note that the females have different sex chromosomes (ZW) and are hemizygous for the Z-linked traits, which means they will express the trait if they carry the dominant allele on their single Z chromosome.