Question

Given below is the representation of a relevant part of the amino acid composition of the β-chain of hemoglobin, related to the shape of human red blood cells.

(a) Is this representation of the sequence of amino acids indicating a normal human or a sufferer from certain blood related genetic diseases? Give reasons in support of your answer.

(b) Why is the disease referred to as a Mendelian disorder? Explain.

Answer 1

(a) The sequence of amino acids in the above representation indicates a normal human. In, the above representation, the 6^th position is occupied by glutamic acid. But if the glutamic acid is substituted by valine at the 6^th position, the person is said to be suffering from sickle cell anemia. It is a disorder in which red blood cells assume an abnormal, sickle-like shape. Such a mutant hemoglobin molecule undergoes polymerization under low oxygen tension to change the shape of red blood cells. 

(b) The mendelian disorder is determined by the alteration or mutation in the single gene. In this disease as well, there is a mutation in a single gene, that too only in the  6^th  position.