a) Sickle cell anaemia is a recessive autosomal disease . It is controlled by a single pair of alleles, HbA and HbS. The defect is caused by point shift mutation i.e. substitution of Glutamic acid by Valine at 6th position of the Beta -Globin chain of haemoglobin molecule.
b) To produce a sickle cell anaemic offspring both of the parent should be a carrier or one should be a carrier and other should be a carrier.
i.e. the genotype should be :
1) HbA, HbS (one parent) and HbA, HbS (other parent)
2) HbS, HbS (one parent) and HbA, HbS (other parent).
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