Answer:
The question lacks options, the options are:
A) one dominant gene for free earlobes.
B) two dominant genes for free earlobes.
C) one recessive gene for attached earlobes.
D) two recessive genes for attached earlobes.
The answer is D)
Explanation:
This is a scenario involving a single gene coding for position of earlobe in humans. The allele for free earlobe (F) is dominant over the allele for attached earlobe (f). This means that in an heterozygous state (Ff), the attached earlobe will be masked by the free earlobe.
This is the case of Ashley's parent which are heterozygous/carriers i.e. they are phenotypically free earlobed but carry the recessive allele (attached earlobe). The free earlobe allele is just masking its expression.
However, their daughter, Ashley, has an attached earlobe. This means that she possesses the recessive trait, which can only be expressed when the recessive allele (attached earlobe) is in a homozygous state i.e. same in the genotype (ff).
Hence, Ashley has two recessive alleles for the attached earlobe (ff), which makes her express the attached earlobe trait.
