Question

Peacock shows which of the following genotypes?
(A) XX
(B) XY
(C) ZZ
(D) ZW

Answer 1

Hint: Birds usually shows the ZZ-ZW system of sex determination, in which ZZ is shown by the males and ZW by the females. Peacock and Peahen ate the male and female versions of the peafowl.

Complete answer:
A peacock is a male peafowl and a Peahen is a female peafowl. In the ZZ-ZW system of sex determination, ZZ chromosomes will be seen in males while ZW chromosomes will be seen in females. This means that a peacock shows the ZZ genotype whereas a peahen shows the ZW genotype.

Additional Information: In contrast to the XY sex-determination system and therefore the X0 sex-determination system, where the sperm determines the sex, within the ZW system, the ovum determines the sex of the offspring. Males here are the homogametic sex (ZZ), while females are the heterogametic sex (ZW).The Z chromosome is always larger and has more number of genes in it, just like the X chromosome within the XY system.

Not a single genes will be shared between the avian ZW and XY chromosomes of the mammals and, from a comparison between chicken and human, the Z chromosome appeared almost like the autosomal chromosome 9 in humans, instead of X or Y, leading researchers to believe that the ZW and XY sex-determination systems don't share an origin, but these sex chromosomes are found to be derived from autosomal chromosomes of the common ancestor. It was thaught that these autosomes possess evolved sex-determining loci that eventually developed into the respective sex chromosomes once the recombination between the chromosomes (X and Y or Z and W) was suppressed.
So, the correct answer is ‘(C) ZZ’.

Note: In Lepidoptera (moths and butterflies), examples of Z0, ZZW, and ZZWW females are often found. This means that the W chromosome is important in the female determination in some species (ZZW), but not in others (Z0).