Which one of the following conditions though harmful in itself, is also a potential saviour from a mosquito borne infectious disease?
- Pernicious anaemia
- Thalassaemia
- Leukemia
- Sickle cell anaemia
Answer
(4) Sickle cell anaemia
Solution
Sickle-cell anaemia is caused by substitution of Glu by Val at the sixth position of the β-globin chain (HbA HbS).
Heterozygous carriers (HbA HbS) are resistant to malaria (a mosquito-borne disease), because the malarial parasite Plasmodium cannot complete its life cycle in their red blood cells.
∴ Though harmful in itself, the sickle-cell gene protects against malaria and is common in malaria-prone regions.
Answer: (4)