Question

Write the type of sex determination mechanism for the following. Give an example of each type.

(i) Female XX and male XO (ii) Female ZW and male ZZ.

Answer 1

1. XX-XO system - It is seen in organisms like crickets, grasshoppers, and some other insects. The female is XX and is the homogametic sex. The male is the heterogametic sex but only has one sex chromosome. The male in XX-XO systems produces gametes with (X) or without (O) a sex chromosome.
   
2. ZZ-ZW system - It is seen in birds. The female is heterogametic i.e. produces ZW gametes, while the male is homogametic and produces only a single type of gamete Z.