question_answer

Haemophilia is a sex-linked recessive disorder of humans. The pedigree chart given below shows the inheritance of haemophilia in a family. Study the pattern of inheritance and answer the questions that follow.

(i) Give all the possible genotypes of the members 4, 5 and 6 in the pedigree chart.

(ii) A blood test shows that the individual 14 is a carrier of haemophilia. The member numbered as 15 got recently married to number 14. What is the probability that their first child will be a haemophilic male?

Answer:

(i) Possible genotype of member 4 is XX or \[X{{X}^{h}}\]

Possible genotype of member 5 is \[{{X}^{h}}Y\]

Possible genotype of member 6 is XY.

(ii) According to the given pedigree, if the member 15 gets married to the member 14 of this family then the probability of first child to be a haemophilia male will be 25%.

Thus, heterozygous female (carrier) for haemophilia may transmit the disease to her sons.