Question

In chickens, the female is the homogametic sex.
A. True
B. False

Answer 1

Organisms have two sexes- male and female. The production of male and female individuals or the formation of male and female reproductive organs forms the basis of sex determination. There are various mechanisms of determination of sex in different groups of organisms. The sex in birds is determined by ZW-ZZ mechanism. In birds, the sex of the embryo is determined by the egg, not the sperm as in humans.

Complete answer:
In chickens, females have a pair of dissimilar sex chromosomes i.e., ZW and are designated as 2A+ZW. Males have two similar chromosomes i.e., ZZ and are designated as 2A+ZZ. The females, therefore, are heterogametic and produce two types of gametes A+Z and A+ W types of gametes. The males are homogametic and produce only one type of gametes.

Hence, the correct answer is option (B).

Additional information:
Avain (birds and chickens) sex is not determined by XX-XY mechanism (like in humans and most mammals) or not even by XX-XO mechanism (as in roundworms and some insects). In XX-XY and XX-XO mechanisms, sex is determined by the sperm which is contributed by male gamete to the offspring.
In contrasts to human and insects, chickens have ZW-ZZ mechanism of sex determination. In ZW-ZZ mechanism, sex of the offspring is determined by the ovum not by the sperm as in XX-XY and XX-XO mechanism.

Note: The various mechanisms of sex determination are as follows:-
XX-XY mechanism:- found in humans and most mammals, (female homogametic and male heterogametic)
XX-XO mechanism:- found in roundworms and some insects, (female homogametic and male heterogametic)
ZW-ZZ mechanism:- found in birds (female heterogametic and male homogametic)
ZO-ZZ mechanism:- found in butterflies and moths ( female heterogametic and male homogametic)