Question

Males are more commonly affected than females in:

• A. Autosomal dominant
• B. Autosomal recessive
• C. X-linked dominant
• D. X-linked recessive

Hint:

A male has only one X, so a single recessive allele is enough.

Answer 1

The Correct Option is D

To find male predominance, look at how the sexes differ in chromosome dosage. A man carries a single X and a Y, so for any gene on the X he has just one copy. A woman carries two X chromosomes, so she has a backup copy of every X-linked gene.

In an X-linked recessive disorder this asymmetry matters a lot. One faulty allele on a man's single X is sufficient to cause disease, since there is no partner X to cover for it. A woman would need the same fault on both of her X chromosomes to be affected, which is uncommon. The result is that males are affected much more frequently. Classic examples are haemophilia, Duchenne muscular dystrophy, and red-green colour blindness.

The other modes do not favour males. Autosomal dominant and recessive genes lie on non-sex chromosomes, so men and women are hit about equally. X-linked dominant disease leans towards females, and in several such conditions affected males die before or soon after birth.

So the inheritance pattern in which men predominate is the X-linked recessive type.
\[\boxed{\text{X-linked recessive}}\]