Question

Given below is a pedigree chart of a family with five children. It shows the inheritance of attached ear-lobes as opposed to the free ones. The squares represent the male individuals and circles represent the female individuals.

Which one of the following conclusions drawn is correct?

• A. The parents are homozygous recessive.
• B. The trait is Y-linked.
• C. The parents are homozygous dominant.
• D. The parents are heterozygous.

Answer 1

Answer: (D)

Human ear lobes can be put under two categories-free and attached. This trait is encoded on autosomal chromosome. The allele for free-hanging earlobes is dominant to the allele for attached earlobes.
In the given pedigree chart we see that both the parents have free earlobes and the offsprings have both free and attached earlobes. This means that the parents must be heterozygous of the trait.
Heterozygous means that a person has two different versions of the gene-a paternal gene and a maternal gene.
Homozygous means that a person has inherited the same version of the gene from each parent.