Why is haemophilia generally observed in human males? Explain the conditions under which a human female can be haemophilic.

Question

Answer the following questions: 

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 M.T.P. It was diagnosed by her doctor that the foetus she is carrying has developed from a zygote formed by an XX egg fertilised by Y-carrying sperms. Why was she advised to undergo M.T.P.?

Answer 1

A. Haemophilia is caused due to the recessive gene on X chromosome. Y chromosome has no allele for this. If a male is X^hY, then he is haemophilic. If male inherits X^h from the mother, he will be haemophilic (with the genotype X^hY). If female inherits X^hX^h , one from the carrier mother and one from her haemophilic father, then she can be haemophilic.

B. Embryo has (trisomy of sex chromosome) XXY karyotype or Klinefelter’s syndrome. 

She was advised to undergo MTP since the child will have the following problems: 

i. male with feminine traits 

ii. gynaecomastia 

iii. underdeveloped testes 

iv. sterile