Question

Explain *** determination mechanism in humans. How is it different in birds?

Answer 1

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In human beings, females are homogametic with X chromosomes only with genetic composition of XX while males are heterogametic with genetic composition of XY. An egg in the female will bear only X chromosome . In males, half the sperms bear X chromosome and the other half bear Y chromosomes. When the X bearing sperm fertilizes the egg, it results in XX forming a female zygote and when a sperm bearing Y chromosome fertilizes the egg, it results in XY condition forming a male zygote. In birds, ZW and ZZ system is followed. Female birds are heterogametic with Z and W chromosomes while male birds are homogametic carrying Z chromosomes in their sperms. In both humans and birds, *** chromosomes are along with the autosomes. In humans, males have 44+XY chromosomes and females have 44+XX chromosomes.

Answer 2

Answer:

The sex chromosomes in birds is determined as Z and W. The male is homomorphic (ZZ) and the female is heteromorphic (ZW). W chromosome carries female sex determining genes and duplication of Z chromosome indicates male sex. So, in case of chicks, the sex is determined by teh egg and not by the sperms.