Question

________ is an example of X-linked recessive trait.

• A. Phenylketonuria
• B. Haemophilia
• C. Cystic fibrosis
• D. Sickle-cell anaemia

Answer 1

Answer: (B)

Haemophilia

• Haemophilia is an inherited bleeding disorder where the blood doesn't clot properly. It is caused when blood does not have enough clotting factor.
• 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.

• In females (who have two X chromosomes), a mutation would have to occur in both copies of the gene to cause the disorder.
• However, in males due to the single copy of X present, there is a greater chance for the disease to manifest.

So, the correct answer is 'Haemophilia'.