Answer:
Probability that their first child will be an albino = 1/4;
Probability that their second child will be an albino is 1/4;
Probability that their third child will have normal pigmentation = 3/4.
Total combined probability of these 3 children = 1/4 x 1/4 x 3/4 = 3/64.
Explanation:
Autosomal recessive disorders are the ones in which disease occurs only if recessive alleles are present in both the locus of a particular gene's allelic positions.
Here both the parents are heterozygous for albinism allele. The probability of allelic combinations of their children is shown as under:
Parentals: Aa x Aa
/ | | \
Progeny: AA Aa Aa aa
The birth of children is independent event so rule of multiplication will be applicable here.
Probability that their first child will be an albino is 1/4 because out of 4 children 1 has the probability of being born with allelic combination 'aa'.
Probability that their second child will be an albino is 1/4 and the reason is same as above.
Probability that their third child will have normal pigmentation is 3/4 because AA, Aa and Aa are 3 children with normal pigmentation.
So the total combined probability is 1/4 x 1/4 x 3/4 = 3/64.
