Answer:
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
