Question

If two parents are both phenotypically normal and DO NOT express the recessive genetic disorder of albinism (a lack of pigmentation) and they produce one offspring that is normal and one that has albinism, what does that tell you about the genotypes of the parents?

Answer 1

The parents show normal phenotype i.e. no albinism, But one of the offspring showed albinism that means both of the parents are heterozygous normal i.e. both are the carriers of albinism gene only then it can become homozygous recessive to express the albinism in one of the offspring.

For example: Let the gene for normal phenotype be 'A' which is dominant and for albinism be 'a' which is recessive.

If the parents are heterozygous normal that they will have the 'Aa' gene each, so the gametes produced by both of them will be A and a.

When we'll cross both the parents following will be the result

	A	a
A	AA	Aa
a	Aa	aa

.From the above punnet square we can see that out of four offsprings one of them is homozygous for albinism and hence will be albino.

If we either of the parents are homozygous normal then none of the offspring will show albinism.

So Both the parents are heterozygous normal i.e. they are the carrier of the albino gene.