Question

Albinism, lack of pigmentation in humans, results from an autosomal recessive gene (a). Two parents with normal pigmentation have an albino child.

(a) What is the probability that their next child will be albino?

(b) What is the probability that their next child will be an albino girl?

(c) What is the probability that their next three children will be albino?

Answer 1

a) 1/4

b) 1/8

c) 1/64

Step-by-step explanation:

Let's assume that the allele "a" is responsible for albinism. The genotype of carrier parents would be "Aa".

a) Aa x Aa = 1/4 AA (Normal): 1/2 Aa (normal) : 1/4 aa (albinic)

Therefore, the probability that their next child will be albino is 1/4

b) In each reproduction, the proportion of a girl child= XX x XY= 1/2 XX (girl) : 1/2 XY (boy)

And the chances of getting an affected child = Aa x Aa= 1/4 AA (Normal): 1/2 Aa (normal) : 1/4 aa (albinic)

Therefore, the probability that their next child will be an albino girl= 1/2 (girl) x 1/4 albinic= 1/8

c) In each reproduction, the chances of getting an affected child = Aa x Aa= 1/4 AA (Normal): 1/2 Aa (normal) : 1/4 aa (albinic).

The chances that their next three children will be albino= 1/4 x 1/4 x 1/4 = 1/64