Question

In humans, having unattached earlobes is the result of a dominant gene, and having attached earlobes is a recessive trait. If a woman with attached earlobes has a child with a man who is homozygous for unattached earlobes, which of the following best describes how the child's earlobes would most likely appear?

a. Their child would have attached earlobes.

b. Their child would have attached earlobes if the father passes on the recessive allele.

c. Their child would have unattached earlobes.

d. Their child would have unattached earlobes if the mother is a carrier for the trait.

Answer 1

Their child would have unattached earlobes.

Step-by-step explanation:

Attached earlobes is a recessive trait and only an individual who is homozygous recessive for this gene will have this trait. Thus the chances of people having unattached earlobes is more than the chances of people having attached earlobes.

Let e denote the gene representing attatched earlobes and E denote unattatched earlobes. When a woman with attached earlobes have a child with a man who is homozygous for unattached earlobes the cross would be represented as

`ee * EE`

F1 generation

eE Unattached

eE Unattached

eE Unattached

eE Unattached

Since e is recessive all the individuals of the F1 generation will have unattached earlobes.

Thus the child will have unattached earlobes.

Answer 2

Homozygous: this means that the man has two genes for unattached earlobes, so whichever of these gene genes is transmitted to the child, it will be unattached. Since having unattached earlobes is a result of a dominant gene, one such gene is enough and the child will definitely have an unattached earlobe.