Question

Sickle-cell anemia helps in the prevention of which disease?
A. Haemophilia
B. Malaria
C. Anemia
D. Thalassemia

Answer 1

Hint: Sickle cell anemia is an autosomal linked recessive disorder which is controlled by a single pair of the allele. The defect is caused as at the sixth position of the beta chain of haemoglobin, the substitution of glutamic acid by valine occurs.

Complete Answer:
(I) Haemophilia: It is a sex-linked recessive trait which is also known as bleeder’s disease. In this, the exposed blood does not readily clot due to the deficiency of plasma thromboplastin in blood.
(II) Malaria: Malaria which is one of the most common diseases of mankind spreads by the bite of female Anopheles mosquitoes. It is caused by the protozoan Plasmodium that requires two hosts two complete its life cycle- man and Anopheles mosquitoes.
(III) Anemia: It is a condition when the blood lacks enough red blood cells which causes decreased levels of oxygen in the blood resulting in tiredness, pale skin, and shortness of breath.
(IV) Thalassemia: It is a group of genetic disorders which result from the defective synthesis of subunits of haemoglobin. It is of two types: alpha-thalassemia and beta-thalassemia.

In sickle cell anemia the mutant haemoglobin molecule undergoes polymerization under low oxygen tension that causes change in the shape of RBC from biconcave disc to elongated sickle cell. These deformed cells prevent the development of Plasmodium in the body so sickle cell anemia helps in preventing malaria.

Note: Haemophilia, sickle cell anemia, thalassemia are examples of Mendelian disorders that are mainly caused due to alteration or mutation in a single gene. These disorders are inherited by offspring from their parents.