(a) Why is haemophilia generally observed in human males? Explain the conditions under which a human female can be haemophilic.
(b) A pregnant human female was advised to undergo MTP. It was diagnosed by her doctor that the foetus she is carrying has developed from a zygote formed by an XX-egg fertilized by Y-carrying sperm. Why was she advised to undergo MTP?

Explanation

(a) The genes for haemophilia are present on the X-chromosome. A male has only one X chromosome and bears only one allele for the trait. He is hemizygous for the trait as Y chromosome does not have a corresponding allele
A female contains two X-chromosomes. She has to be homozygous recessive It means her father must be a sufferer and mother either a carrier or sufferer to be affected by the disease.
(b) The zygote will have XXY-chromosomes. It will develop into a male with Klinefelter's syndrome. Such males are sterile and show feminine characters. That is why the female is advised to undergo MTP