Question

A genetic disease in many Africans which reduces the oxygen uptake by RBC is known as:
A. Sickle cell anaemia
B. Anaemia
C. Pernicious anaemia
D. Haemophilia

Answer 1

Hint: Lack of awareness or due to some cultural forces, individuals in a population are driven to form consanguineous relationships. The outcome of these relationships is an increase in homozygosity of alleles. This homozygosity present in recessive forms makes the population prone to any diseases.

Complete Step by Step Answer:
Sickle cell anaemia is a point mutation which is inherited genetically. It results from the replacement of the seventh codon of the gene sequence. This change results in the production of amino acid Valine in place of Glutamic acid. The physiological effect that it has is qualitative. It turns the biconcave shaped red blood cells to sickle shaped cells. This shape leads to less oxygen uptake by red blood cells. It is present in most Africans due to lack of awareness of certain medical facilities like studying the karyotype of parents before pregnancy; marriages performed in bloodline which increases homozygosity. Although it can be fatal, it is a boon in some form. People who are carriers of sickle cell anaemia are resistant to malaria.

Anaemia is a broad term that includes all those diseases which make it difficult for red blood cells to deliver oxygen. It can include both quantitative and qualitative factors like Thalassaemia and Sickle cell anaemia respectively. It can be due to genetic factors as stated previously or due to nutritional deficiencies. For example, lack of sufficient Iron in diet.

Pernicious anaemia is a disease caused by nutritional deficiency of vitamin B12. This could also be caused by an autoimmune disease that does not allow one to produce the intrinsic factor. This intrinsic factor is essential to absorb vitamin B12 that one consumes. The vitamin further is necessary for the efficient functioning of red blood cells.

Haemophilia is an X linked disease. It is caused by mutation which results in lack of blood clotting factors especially factor 8. Thus, if a haemophilic person undergoes any accident that breaks the barrier of skin and the blood flows out, there will be a huge blood loss since its body is not capable of clotting the blood.

Thus, the correct answer for this question is A: Sickle cell anaemia

Note: Since the allele for sickle cell anaemia is recessive, it requires homozygosity to occur. If a person has only one allele, he/she will be attributed as a carrier but they would not show symptoms of this disease. Although they play a role in transmitting this gene if they choose to breed and produce offspring.