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

Step 1: The question asks which inheritance pattern shows a clear male predominance among affected people.
Step 2: Males have only one X chromosome (XY), so they are hemizygous for X-linked genes. A single recessive mutant allele on the X is enough to make a male affected, because he has no second X to mask it.
Step 3: A female (XX) needs the mutant allele on both X chromosomes to be affected by an X-linked recessive disease, which is far less likely. So in X-linked recessive conditions (for example haemophilia A and B, Duchenne muscular dystrophy, red-green colour blindness) males are affected much more often than females.
Step 4: Why the others are wrong. Autosomal dominant and autosomal recessive disorders affect both sexes roughly equally because the genes are not on the sex chromosomes. X-linked dominant conditions actually tend to affect females more often or to be lethal in males, the opposite of male predominance.
Step 5: Therefore the pattern with male predominance is X-linked recessive.
Answer: Option D (X-linked recessive).