Question

10 consider the pedigree to the right.
(a)

part a
what type of inheritance is displayed?
a autosomal recessive
b sex - linked dominate
c sex - linked recessive
d autosomal dominant

Explanation:

• Autosomal recessive: If it were autosomal recessive, both parents (I - generation) would need to be carriers (heterozygous) to have an affected child (II - generation). But here, the female in II - generation is affected. If it were autosomal recessive, the unaffected parents (I - generation) would have to be carriers. However, let's check other options.
• Sex - linked dominant: In sex - linked dominant inheritance, an affected female (in II - generation) would pass the trait to all sons (in III - generation). But the son in III - generation is unaffected. So this is not sex - linked dominant.
• Sex - linked recessive: In sex - linked recessive inheritance, for a female (in II - generation) to be affected, her father (in I - generation) should be affected (since he has only one X - chromosome). But the father (in I - generation) is unaffected. So this is not sex - linked recessive.
• Autosomal dominant: In autosomal dominant inheritance, an affected individual (II - generation female) can have an unaffected parent only if there is a new mutation, but more likely, if we assume that the parents (I - generation) are both heterozygous (unlikely as per the pedigree simplicity assumption for such questions, but when we rule out other options). Also, an affected female (II - generation) can have an unaffected son (III - generation) as the son can inherit the recessive allele from the father (II - generation male).

Answer:

D. Autosomal dominant