Question

An uncommon genetic mutation in the human population is in the gene that codes for glucose 6-phosphate dehydrogenase, the enzyme that catalyzes the first and rate-limiting step of the pentose phosphate pathway. Individuals that inherit this mutation are often protected against developing malaria. This is because they are unable to effectively remove reactive oxygen species (ROS, i.e., superoxide radical, hydrogen peroxide, and hydroxyl radical) and thus the protozoan (Plasmodium falciparum), which infects red blood cells causing malaria, is destroyed by ROS. Why would a mutation causing a defective or inactive glucose 6-phosphate dehydrogenase protect these individuals from malaria?

Answer 1

Answer: Because some mutations can exert selection pressure on some mutations, selecting them positively in order to perpetuate the species.

Explanation:

Malaria may have exerted selection pressure on the human genome, causing it to evolve by selecting those genes that provide this resistance to the Malaria disease, prevailing against the negative effect of the mutation itself. Therefore, this phenomenon is seen in populations where mutation of the gene that codes for glucose 6-phosphate dehydrogenase is common, for example in some african pupulations.