If a man who is a carrier for sickle-cell anaemia marries a carrier woman. What are the chances of this couple having an affected offspring?

The correct option is C 25%
Genotype of normal individual: AA
Genotype of affected individual: SS
Genotype of carrier man and woman: AS


The cross will be as follows:



The possibilities are as follows:
Affected offsprings: 25% or$\left(\frac{1}{4}\right)$
Carriers: 50% or$\left(\frac{2}{4}\right)$
Normal offsprings: 25% or$\left(\frac{1}{4}\right)$