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Class 12th Biology 2018 Set1 Delhi Board Paper Solution

Question 15

Explain the mechanism of ‘sex determination’ in birds. How does it differ from that of human beings?


In birds, sex determination is of  ZW-ZZ type.

In this type of homogametic and haven ZZ sex chromosomes and females are heterogametic with ZW pair of sex chromosomes.

Parents :                  Male            X               Female

                                 ZZ                                  ZW

Gametes :                (Z) (Z)                             (Z) (W)

Tr :                          Female                            Male

Where as in humans,the chromosomal mechanism of sex determination is XX-XY type. The human male is heterogametic and  have XY sex chromosome and human female is homogarnetie with XX sex chromosomes.