Principles of Inheritance and Variation Question 194
194. Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino?
(a) 25%
(b) 50%
(c) 75%
(d) 100%
Show Answer
Answer : a
Hints & Solution
(a) A child will be albino only if it is homozygous for albinism genes (since albinism is a recessive character). As parents have normal skin, it means they are heterozygous. As a result of cross between two heterozygous parents, 25% of the children will be homozygous recessive. The nature of the second child is not affected in any way by the nature of the first child because both are independent events.
