Using an example, explain an effect of gene mutation in humans.

In this questions, first show your understanding of the term gene mutation. Then using suitable examples outline the effect of this process in humans.

A gene mutation is a sudden irreversible change in the structure of a gene. It is also called point mutation. It results in loss or change of function of the gene in question. Gene mutation is the cause of some of the disease called genetic disease. Example is sickle cell anemia;

This is caused by a mutation in the gene responsible for synthesis of β – polypeptide chains in hemoglobin.

This results in replacement of glutamine with valine in position 6 of the chains, leading to formation of hemoglobin S.

The condition has the following effects.

• Hemoglobin S crystallizes at low oxygen tensions, making the red blood cells fragile and to adopt a sickle shape. They can hardly pass through capillaries and the spleen sinusoids.
• The red blood cells become more easily hemolyzed in the liver and spleen. This reduces the number of red blood cells causing anemia.
• Bilirubin, the bi-product of hemoglobin breakdown, accumulates in the body and causes yellowing of the body surface membranes especially the sclera (jaundice)

Note: other conditions that occur due to gene mutation include;

• Alkaptonuria
• Phenylketonuria
• Albinism