Zoology - Principles of Inheritance and Variation Question with Solution | TestHub

Sickle Cell Anemia is an autosomal recessive trait. And it is caused by an error in the gene for haemoglobin, a protein which transports oxygen in the bloodstream. The gene defect is a known mutation of a single nucleotide (see single-nucleotide polymorphism - SNP) (A to T) of the β-globin gene, which results in glutamic acid being substituted by valine at position 6. Haemoglobin S with this mutation is referred to as ${\text{Hb}}^{\text{S}}$ , as opposed to the normal adult ${\text{Hb}}^{\text{A}}$ .Out of the three possible genotype only homozygous individuals for  ${\text{Hb}}^{\text{S}}{\text{Hb}}^{\text{S}}$  show the diseased phenotype.Heterozygous  ${\text{Hb}}^{\text{A}}{\text{Hb}}^{\text{S}}$ individuals appear apparently unaffected but they are carrier of the disease.