Question

Haemophilia and red-green colour blindness are:

• A. X-linked dominant disease.
• B. X-linked recessive disease.
• C. Y-linked dominant disease.
• D. Y-linked recessive disease.

Answer 1

The correct option is B X-linked recessive disease.

Hemophilia and red-green colour blindness are inherited in an X-linked recessive pattern.
A condition is considered X-linked when gene mutation that causes it is located on the X chromosome.
In male, one altered copy of the gene in each cell is enough to cause the condition.
Since females have two X chromosomes, a mutation must be present in both copies of the gene to cause hemophilia.
Males are affected by X-linked recessive disorders much more frequently than females.
A major characteristic of X-linked inheritance is that fathers cannot pass X-linked traits to their sons.