Question

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene designated 'a'. Parents with normal pigmentation have an albino child. What is the possibility that their next child be albino? What is the possibility that the next child will be an albino girl?

• A. 1/4; 1/2
• B. 1/2; 1/4
• C. 1/4; 1/8
• D. 1/8; 1/4

Answer 1

Answer: (C)

The correct option is C 1/4; 1/8
Albino is an autosomal recessive disorder and should be present in the homozygous state (aa) to express itself. Since normal parents have an albino child (aa), this means that both parents carry one copy of albino allele (a) and are the carrier for the disease. The heterozygous parents (Aa) will produce genotypic ratio 1 AA: 2Aa: 1 aa which makes that there is always ¼ possibility of their child to be albino. Since each time a couple can have ½ sons (XY) and ½ daughters (XX); therefore, the heterozygous couple will have ¼ x ½ = 1/8 possibility of their girl child to be albino.

So, the correct answer is option C.