A couple, both of whom are carriers for sickle cell anaemia, are planning to have a child. What is the probability that their child will produce beta-globin chains exclusively having Valine at the sixth position?

Step-by-step solution

Sickle cell anaemia is an autosomal recessive disorder. The parents are carriers, meaning their genotype is Hb^ A Hb^ S . They produce both normal beta-globin chains (with Glutamic acid) and mutant beta-globin chains (with Valine). A child whose beta-globin chains exclusively have Valine at the sixth position must be homozygous for the mutant allele, possessing the genotype Hb^ S Hb^ S . When two heterozygous carriers are crossed ( Hb^ A Hb^ S Hb^ A Hb^ S ), the probability of the offspring inheriting the mutant al