Question

How is it possible for an offspring to exhibit a recessive trait if neither parent exhibited that recessive trait? What must be true about the parents’ genes for this to occur?

Answer 1

Hello!

I will use a capital letter to demonstrate dominant (B) and lowercase letter to demonstrate recessive (b).

The given scenario would only be possible of both of the parents had heterozygous genes (Bb), meaning that they have one dominant allele and one recessive allele.

The offspring will only exhibit a recessive trait if that particular gene has two recessive alleles (bb). If both parents have only one recessive allele (Bb), then neither will exhibit the recessive trait.

It is possible, however, that each parent will pass on their one recessive allele. In this case, the offspring would now have two recessive alleles (bb) and begin exhibiting the recessive trait.

I hope this helps!

Answer 2

Answer: it is possible for an offspring to exhibit a recessive trait if neither parent exhibited that recessive trait if both parents are heterozygous for the trait. The parents' genotype must be heterozygous i.e., having one dominant allele and one recessive allele.

Explanation: It is possible for an offspring to exhibit a recessive trait when neither of the parents exhibited the recessive trait.

For example, if (A) is the allele for normal skin colour and it is dominant to (a) which is the allele for albinism that is recessive, two parents with heterozygous genotype Aa will have offsprings with the following possible genotypes: Aa x Aa = AA, Aa, Aa and aa.

One of the offsprings will inherit recessive allele for albinism from each parent (aa), and thus will manifest outwardly as albino child.