Question

The possibility of a female becoming haemophilic is extremely rare because the mother of such a female has to be at least (i) and father should be (ii).
A. (i) Haemophilic, (ii) Carrier
B. (i) Carrier, (ii) Haemophilic
C. (i) Haemophilic, (ii) Normal
D. (i) Haemophilic, (ii) Haemophilic

Answer 1

Hint: Haemophilia is a rare genetic condition where the individual experiences a distorted blood clotting mechanism. It is also known as The Royal disease because it affected the royal families of England, Germany, and Russia. In this, the males are mostly affected while females may lead a normal life even when they have defective genes on one of their X chromosomes.

Complete answer:

Haemophilia is an inherited recessive sex-linked genetic disorder. In this condition, the person lacks the blood clotting factors. Thus, such individuals show prolonged bleeding even from minor injuries. In females, there are XX chromosomes whereas in males it is XY. So, a female is hemophilic (or said to be affected with haemophilia) if she has both the X chromosome and possesses the defective gene responsible for hemophilia. However, a male is found to be haemophilic if he has the defective gene for haemophilia on his X chromosome, causing the individual to lack factors essential for blood clotting. 

A female with the defective gene on only one of the X chromosomes is normal, and said to be only a carrier for this genetic disorder (haemophilia) because the other X chromosome has the gene for normal blood clotting. Therefore, a female is haemophilic only when she has homozygous recessive genes for the trait, that is, her father must be haemophilic contributing for providing one defective paternal X chromosome, and mother must be at least a carrier to provide another X chromosome with a defective gene responsible for hemophilia.

Thus, the correct answer is option B. The availability of another X chromosome in females makes them less prone to Haemophilia. The father must be affected with haemophilia, and the mother should at least be a carrier for the disorder so as to have a haemophilic daughter.

Hence, the correct answer is option (B).

Note: Haemophilia is a rare inherited condition where the individual lacks the blood clotting abilities. The factors responsible for blood clotting are absent in such individuals and thus, this can often lead to serious blood loss in injured situations, severing the consequences further.