Question

The daughters born to haemophilic father and normal mother could be

• A. Normal
• B. Carriers
• C. Haemophilic
• D. All of the above

Answer 1

Answer: (B)

Carriers

Haemophilia is a X-linked recessive disorder. Since, males are hemizygous for chromosome, one copy of the affected gene in each cell is sufficient to cause the disorder (X${}^h$Y). Females have two X chromosomes and hence need two copies of the affected gene to cause the disorder (X${}^h$X${}^h$). Females heterozygous (X${}^h$X) for this trait be normal but serve as a carrier of the disease. According to the question, man has haemophilia (X${}^h$Y) and woman is normal (XX).
Parent generation : XX x X${}^h$Y

Gametes : XX --> X${}^h$Y	X	X
X${}^h$	X${}^h$X carrier girl	X${}^h$X carrier girl
Y	XY normal boy	XY normal boy

F${}_1$ generation = 1 normal carrier girl : 1 normal boy
Thus, the correct answer is option B.