Albinism is an inherited condition caused by a recessive allele a. A is the dominant allele for the normal condition. What are the genotypes of individuals R and S?

R = AA, S=AA

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R = AA, S=Aa

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R = Aa, S=Aa

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R = aa, S=aa

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Solution

The correct option is B R = Aa, S=Aa
In generation 1, the albino male and albino female will have their genotype as " $a a$ " (recessive allele for albinism).
In an autosomal recessive pedigree, normal male and female may have their genotype as " $A A$ " or " $A a$ ".
All children in generation 2 are normal. Hence, their genotypes will be " $A a$ " because one of their parent is affected and can only transfer recessive allele to their children.
In generation 3, there are 7 children (2 normal males, 3 normal females, 1 albino male, and 1 albino female).
The genotypes of normal children will be " $A a$ ", whereas that of albino children will be " $a a$ ". R and S belong to generation 2, where all the children are normal with their genotype as " $A a$ ".

So, the correct answer is option C.

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