Question

Which disorder is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the hemoglobin?

• A. Phenylketonuria
• B. Sickle-cell Anemia
• C. Hemophilia
• D. Thalassemia

Answer 1

The Correct Option is B

The disorder caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the hemoglobin is known as Sickle-cell Anemia. 

In the normal beta-globin chain of hemoglobin, the sixth amino acid is Glutamic acid. In Sickle-cell Anemia, due to a genetic mutation, Glutamic acid is replaced by Valine. This substitution leads to the production of abnormal hemoglobin known as hemoglobin S (HbS).

Explanation of the mutation process:

• Normal hemoglobin (HbA): In a healthy individual, the beta-globin chain sequence includes Glutamic acid at the sixth position. This ensures the normal disc shape of red blood cells and their functionality.
• Mutant hemoglobin (HbS): The mutation from Glutamic acid (hydrophilic) to Valine (hydrophobic) causes hemoglobin to polymerize under low oxygen conditions, leading to distorted sickle-shaped red blood cells.
• These sickle-shaped cells cause blockages in blood vessels and are prone to destruction, resulting in anemia and various complications associated with Sickle-cell Anemia.

This genetic disorder illustrates the importance of amino acid sequencing in protein function and the profound impact that a single amino acid substitution can have on overall health.

Answer 2

Sickle-cell anemia is a genetic disorder caused by a mutation in the beta-globin gene of hemoglobin. Specifically, it involves the substitution of the amino acid glutamic acid (Glu) with valine (Val) at the sixth position of the beta-globin chain. This small change leads to the formation of abnormal hemoglobin, known as hemoglobin S (HbS), which causes red blood cells to adopt a sickle shape, leading to reduced oxygen-carrying capacity and blockages in blood vessels.

• Phenylketonuria is caused by a defect in the enzyme phenylalanine hydroxylase.
• Hemophilia is a bleeding disorder caused by a deficiency in clotting factors.
• Thalassemia involves reduced or absent production of one of the globin chains of hemoglobin, but it does not result from the glutamic acid to valine substitution.