Question

An individual has two copies of a sickle-cell allele of hemoglobin in which a (historical) mutation replaced the underlined A (see above) with a T. Explain how this change in genotype causes a change in phenotype. For full credit, address (1) the sequence of the protein, (2) the three-dimensional structure of the protein, and (3) the consequences for the red blood cells and the individual.

Answer 1

This change in one nucleotide produces a change in the amino acid sequence. Because of this a glutamine is changed to valine a hydro phobic amino acid at 6th position. This is called HbS sickle cell anemia haemoglobin. In high oxygen this hemoglobin works just fine and there is no change in the structure of the protein. But in low oxygen, this hemoglobin polymerizes with each other leading to formation fibrous patches. These fibrous patches consequently change the shape of the RBCs into a sickle shaped cell