Question

Earlobes can be either attached or detached the allele for attached earlobes is recessive and the allele for detached earlobes is dominant what must be true if a boy is born with attached earlobes?

Answer 1

The correct answer would be "he must be homozygous recessive".

As attached earlobes is a recessive trait, it requires the presence of two copies of the recessive allele in order to produce the specific trait.

Thus, the boy must be homozygus recessive for the trait.

In addition, it is possible only in three cases that the boy can have attached earlobes:

Both the parents have attached earlobes.

Both the parents are heterozygous for the trait.

One parent is homozygous recessive and other is heterozygous for the same.

Answer 2

The boy is homozygous recessive for the trait (attached earlobes)

Since the allele for attached earlobes is recessive he must have two copies of it making him homozygous recessive.