Question

the pedigree below represents an inherited disorder.

what mode of inheritance is shown?
a autosomal recessive
b x - linked recessive
c x - linked dominant
d autosomal dominant

Explanation:

• Autosomal recessive: Requires two recessive alleles. Not clearly indicated here.
• X - linked recessive: Males (with one X) are more affected. In the pedigree, males are affected and females can be carriers (as per the key), which fits X - linked recessive traits. Males get the X from mother. If mother is carrier (heterozygous), sons have 50% chance.
• X - linked dominant: Would show more widespread expression, not just males affected with carrier females.
• Autosomal dominant: Would show more consistent presence across generations without the male - specific (due to single X) pattern.

Answer:

B. X - linked recessive