Question

Two humans mate who are heterozygous for earlobe shape where attached earlobes (A) are dominant to free earlobes (a), and earwax quality where dry earwax (e) is recessive to wet earwax (E ). What is the probability that their first child will have dry earwax and attached earlobes

Answer 1

3/16

Step-by-step explanation:

This question involves two different genes coding for earlobe shape and earwax quality. The alleles for attached earlobes (A) and wet earwax (E) are dominant over the alleles for free earlobes (a) and dry earwax (e).

According to this question, two humans mate who are heterozygous for both genes i.e. AaEe × AeEe. Each parent will produce the following gametes: AE, Ae, aE, ae.

Using these gametes in a punnet square (see attached image), the following proportion of offsprings will be produced:

* Attached earlobe, wet earwax (A_E_) = 9/16

* Attached earlobe, dry earwax (A_ee) = 3/16

* Free earlobe, wet earwax (aaE_) = 3/16

* Free earlobe, dry earwax (aaee) = 1/16

Hence, the probability of these parents having their first child with dry earwax (ee) and attached earlobes (A_) i.e. genotype A_ee is 3/16.