CBSE Class 12-science Answered

The XY type of sex determination is seen in humans. Both males and females have equal number of chromosomes. Males have one X chromosome and a smaller Y chromosome, while females have a pair of X chromosomes. Hence, males have autosomes and XY sex chromosomes, while females have autosomes and XX sex chromosomes. This shows male heterogamety.

Female heterogamety is observed in birds. They exhibit ZW type of sex determination. Both males and females have equal number of chromosomes. Female birds have one Z and one W chromosome, whereas males have a pair of Z chromosomes.