What is the heterozygous advantage of people having sickle cell trait in areas where malaria a major cause death?

In areas where malaria is a major cause of death, individuals who carry the sickle cell trait (heterozygous for the sickle cell gene) have a heterozygous advantage. This means that they have a selective advantage over individuals who do not carry the trait.

Malaria is a parasitic infection that is transmitted by the bite of an infected female Anopheles mosquito. The parasite, Plasmodium falciparum, enters the bloodstream and infects red blood cells. In individuals with sickle cell trait, the abnormal shape of their red blood cells makes it more difficult for the malaria parasite to invade and reproduce within them. As a result, individuals with sickle cell trait are less likely to develop severe malaria and are more likely to survive.

The heterozygous advantage of sickle cell trait is particularly pronounced in areas where malaria is highly prevalent and where the strain of malaria parasite is particularly virulent. In these areas, individuals with sickle cell trait may have a significantly reduced risk of death from malaria compared to individuals who do not carry the trait.

The heterozygous advantage of sickle cell trait is an example of how natural selection can act on a population. In this case, the selective pressure is the presence of a deadly disease, malaria. Individuals who carry the sickle cell trait have a better chance of surviving and reproducing in this environment, and as a result, the frequency of the sickle cell gene increases in the population over time.