A cross between a normal couple resulted in a son who was haemophilic and a normal daughter. In course of time, when the daughter was married to a normal man, to their surprise, the grandson was also haemophilic.

(a) Represent this cross in the form of a pedigree chart. Give the genotypes of the daughter and her husband.

(b) Write the conclusion you draw of the inheritance pattern of this disease.

(a)

Genotype of daughter: XX

Genotype of her husband: XY

(b) This chart shows the transfer of a sex-linked recessive disorder called Haemophilia. It is transferred from carrier female to the male child.

This pedigree chart shows the carrier female transferring the disease to her daughter and son. This makes the daughter a carrier of the disease and her son a haemophilic. The grandson of the carrier daughter also has Haemophilia.