Question

Albinism is a genetic disorder caused by an autosomal recessive allele. The dominant allele results in the wildtype pigmentation.

a) If an albino marries a homozygous person for the wildtype pigmentation allele, what would be the expected phenotype and genotype of their children?

b) If an albino marries a person with wildtype pigmentation but that carries the albino allele, what would be the expected phenotypes and genotypes of their children?

c) Two parents of wildtype pigmentation had an albino child. How is this possible? Indicate the genotypes of the parents.

Answer 1

a)Since albinism is caused by recessive allele, let genotype be represented by aa for albino. Genotype for homozygous wild type( without 'a'allele) is AA.

M/F	a	a
A	Aa	Aa
A	Aa	Aa

Expected Genotype is Aa

Expected phenotype is wild type pigmentation(because offspring would carry only one albino allele).

b) A person who carries the albino allele but displays wild type pigmentation, is said to be a carrier with genotype Aa. Albino genotype aa.

M/F	a	a
A	Aa	Aa
a	aa	aa

Expected Genotype is : Aa, aa

Expected phenotype is : wild type pigmentation 50%, albino 50%

c)This is possible if both the parents are carriers. A person who carries the albino allele but displays wild type pigmentation, is said to be a carrier with genotype Aa.

M/F	A	a
A	AA	Aa
a	aa	aa

Expected phenotype is : wild type pigmentation 50%, albino 50%