What is the common mutation in sickle cell anemia What are t

What is the common mutation in sickle cell anemia? What are the consequences of this mutation biologically?

Solution

Answer : Missense mutation is the coomon mutation found in sickle cell individuals.

Missense mutation brings about the alteration in the codon so as to produce an altered amino acid in the protein.

In humans a single nucleotide change in codon six in the beta hemoglobin chain (GAG – Glutamate) ----- (GUG – valine). By this if an individual is a homozygous he or she will have sickle shape anemia. The altered properties of hemoglobin S result from a single amino acid substitution, a Val instead of a Glu residue at position 6 in the two beta chains. The R group of valine has no electric charge, whereas glutamate has a negative charge at pH 7.4. Hemoglobin S therefore has two fewer negative charges than hemoglobin A, one for each of the two chains. Replacement of the Glu residue by Val creates a “sticky” hydrophobic contact point at position 6 of the chain, which is on the outer surface of the molecule. These sticky spots cause deoxyhemoglobin S molecules to associate abnormally with each other, forming the long, fibrous aggregates characteristic of this disorder.