Question

For each of the following pedigrees, give the mostly likely mode of inheritance. Explain your reasoning.

Answer 1

a)

Autosomal dominant inheritence

Reasons:

• both male and female transfer the disease vertically.
• only one allele is sufficient to express the disease
• moreover disese is transferred from male to male and expressed equally in male and female

b)

Autosomal recessive inheritence

Reasons: both recessive alleles are required for expression of gene. In this case, the generation II has parents of which one is homozygous for recessive allele (causing disease) and other is homozygous normal. As a result we don't see any diseased offspring in generation II. However, generation II are carriers of recessive allele. When the offsprings of generation II mate with normal individuals, there is chance of getting generation III which are again carriers. But when offsprings of generation III mate among themselves, the recessive alleles can come in homozygous form, thus expressing disease. This can happen both in male and female offspring equally.