Consider the following family history:

Question

Bob has a genetic condition that affects his skin.
Bob’s wife, Eleanor, has normal skin. No one in Eleanor’s family has ever had the skin condition.
Bob and Eleanor have a large family. Of their eleven children, all six of their sons have normal skin, but all five of their daughters have the same skin condition as Bob.

Based on Bob and Eleanor’s family history, what inheritance pattern does the skin condition most likely follow?

View Available Hint(s)for Part A

X-linked dominant
X-linked recessive
autosomal recessive
autosomal dominant
Y-linked

Answer 1

Based on the family history provided, the skin condition that Bob has is most likely X-linked recessive.

Here's the reasoning:

1. Bob, who has the skin condition, has normal sons and affected daughters. If the condition is X-linked recessive, Bob would pass his Y chromosome to his sons (which is why they have normal skin, inheriting the normal X chromosome from their mother) and his X chromosome with the condition to his daughters, which would result in all daughters being affected.

2. Since Eleanor has normal skin and no one in her family has the condition, it indicates she does not carry the allele for the skin condition. Therefore, when Bob (with the condition) and Eleanor (without the condition) have children, the daughters inherit Bob's affected X chromosome (resulting in the condition) and the normal X chromosome from Eleanor.

Therefore, the inheritance pattern is consistent with X-linked recessive.