NEET BIOLOGY

Detailed explanation-1: -The sex chromosomes in birds are designated Z and W, and the male is the homomorphic sex (ZZ) and the female heteromorphic (ZW). In most avian species the Z chromosome is a large chromosome, usually the fourth or fifth largest, and it contains almost all the known sex-linked genes.

Detailed explanation-2: -In this system the genetic sex of an offspring is determined by a pair of sex chromosomes, always a Z from the father, and either a Z or W from the mother. The ZW system is opposite of the XY system in that the mother’s sex chromosome determines the genetic sex of the offspring.

Detailed explanation-3: -The sex of birds is determined by inheritance of sex chromosomes at fertilization. The embryo with two Z chromosomes (ZZ) develops into a male; by contrast, the embryo with Z and W chromosomes (ZW) becomes female.

Detailed explanation-4: -The W and Z chromosomes probably share large homologous segments that can recombine, except in the region of the female sex factor on W (tf gene).