15.Albinism in humans is autosomal and fully recessive to normal color. A couple, who are both normal, have a daughter who is albino and a son who is normal. e couple wants to have 3 more children. What is the probability that they will have 3 normal girls

27/512

Explanation:

Let the allele for albinism be represented by a (since it is recessive), the normal skin color allele would then be A.

A normal person would have either AA or Aa genotype. The Aa, even though normal in appearance is carrying the albinism allele and is known as a carrier of the trait.

For a normal couple to have given birth to a son with albinism, it means they are both a carrier of the trait (Aa).

Crossing the two individuals in marriage:

        Aa    x    Aa

    AA   Aa   Aa   aa

The probability of giving birth to an albino is, therefore, 1/4 while that of giving birth to a normal individual is 3/4. These probabilities remain the same for every potential birth irrespective of the number of children they already have.

The probability of given birth to a boy or a girl is 1/2 for every potential birth.

The probability of having a normal boy/girl would be 1/2 x 3/4 = 3/8

Hence, the probability of having 3 normal girls in their next 3 children would be: 3/8 x 3/8 x 3/8 = 27/512

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