Question

Explain chromosomal sex determination mechanisms with examples

Answer 1

Sex of the baby depends upon the Chromosome. Male gamete sperms contains "X" and "Y" Chromosome whereas female gamete egg contains only "X" Chromosome. In case sperms carrying X chromosome fuses with egg having X chromosome then zygote formed will result in female child. If sperm contains Y chromosome and fuses with egg having X then zygote formed will result in male child.

Answer 2

Answer:

According to chromosomal theory of sex-determination, the male and female individuals normally differ in their  chromosomal constituent. On this basis in diploid organisms, there are two types of system.

• System in which male is heterogametic

• System in which female is heterogametic  

In the first system, the female have XX-chromosomes while male have XY-chromosomes because of which  males produce two types of sperms i.e. 50% carry X-chromosome and 50% carry Y-chromosome.

This chromosomal pattern varies in different organism in the way that male either contain Y-chromosome  (i.e., XX-XY system) or contain no chromosome along with X-chromosome (XX-XO type).

XX-XY method is the most common method and is found in human, Drosophila. In this system female is  homogametic and male is heterogametic i.e. two type of sperm (50% carry X-chromosome) and 50% carry  Y-chromosome. Sex of embryo depends upon the kind of sperm.

XX-XO method is found in insects  (grasshopper). Again male is heterogametic i.e. 50% sperm has X-chromosome while 50% without any sex  chromosome. In males, Y-chromosome is absent.

In the second system ZW-ZZ method and ZO-ZZ method i.e., female is heterogametic (ZW) and male is  homogametic (ZZ). ZW-ZZ type is found in birds and ZO-ZZ type in butterflies.