EVERYDAY SCIENCE

Detailed explanation-1: -The boy will have only X and Y chromosomes, where only X can carry genes. The X chromosome will come from mother who produces two kinds of gametes-with normal X chromosome and defective one. Thus, there is 50% chance for the son to have the disease as well as, not to have the disease.

Detailed explanation-2: -So, the correct answer is ‘A male offspring has 50% chance of active disease’.

Detailed explanation-3: -Haemophilia is a sex-linked recessive disease. The defective genes present on the X chromosome only and not on the Y chromosome. As the father always contributes a Y chromosome and never passes an X chromosome to his son, the gene for haemophilia can never be passed from a father to his son.

Detailed explanation-4: -Inheritance. Hemophilia A and hemophilia B are inherited in an X-linked recessive pattern . The genes associated with these conditions are located on the X chromosome, which is one of the two sex chromosomes .

Detailed explanation-5: -There is no chance that a son will be haemophilic if his father is haemophilic because a father passes only the Y chromosome to a boy and the X chromosome to a girl so only girls are affected if a father is haemophilic. Q.