Question

Which of the following most appropriately describes haemophilia?

• A. Recessive gene disorder
• B. X – linked recessive gene disorder
• C. Chromosomal disorder
• D. Dominant gene disorder

Answer 1

The correct option is B X – linked recessive gene disorder

Haemophilia is a inherited X-linked recessive gene disorder that impairs the body's ability to make blood clots.
X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome.
Females have two X chromosomes; males have one X and one Y. Genes on the X chromosome can be recessive or dominant. Their expression in females and males is not the same. Genes on the Y chromosome do not exactly pair up with the genes on the X chromosome.
X-linked recessive genes are expressed in females only if there are two copies of the gene (one on each X chromosome). However, for males, there needs to be only one copy of an X-linked recessive gene in order for the trait or disorder to be expressed.