Question

A husband and wife want to have 5 children however they are both carriers of the autosomal recessive allele for cystic fibrosis. Showing working calculate each of the following parts:

a) the probability of having all five children affected by cystic fibroisis

b )the probability of having only two affected children

c )the probability of having at lest three of their children affected

PLEASE NOTE THIS IS NOT A MULTIPLE CHOICE THERE ARE THREE DIFFERENT PARTS OF THE QUESTION.

Answer 1

Ans

a) If both carriers of the autosomal recessive allele for cystic fibrosis, the probabilty of each children affected = 1/4

So, the probability of having all five children affected by cystic fibroisis = 1/4 × 1/4 × 1/4 × 1/4 × 1/4 = 1/ 1024

b) The probability of having only two affected children = 1/4 × 1/4 = 1/ 16.

c) The probability of having at lest three of their children affected = 1/4 × 1/4× 1/4 = 1/ 64.