Balanced Polymorphism, Essay Example

A definition and description of the term “balanced polymorphism” follows.  The discussion is augmented citing phenomena in malarial and non-malarial environments.

Balanced polymorphism means an organization of genes in which two alleles are preserved in steady balance because the heterozygote is more robust than the individual homozygote.

Although ordinary variety eradicates harmful phenotypes the gene pool, harmful alleles persist. Genetic diseases linger when heterozygosis advantages certain individuals. A good example is that of sickle cell in malarial environments. Malaria is an infectious parasite that is transported from mosquitoes to humans through the blood stream. The parasite invades red blood cells, multiply and burst the cells to spread the disease within the body. Those with one copy of the sickle cell allele have red blood cell membranes that do not allow the malaria parasite to enter the cell. This demonstrates balanced polymorphism those with the sickle cell gene are more resistant to malaria. Sickle cell carriers endure mild cases of malaria which help them survive better in malarial environments.

People with many sickle cell carriers are not debilitated by malaria. They remain strong enough through infection to survive the illness much better than normal people. As such, sickle cell is more common in agricultural societies because clearing land generally encourages mosquito populations. This spreads malaria and advantages those with the sickle cell allele. The price is that if two people with one sickle cell allele have kids, those kids have a 25% of have sickle cell anemia. In non-malarial environments, there is no advantage for the sickle cell allele and, thus, it is much less common.

Balanced polymorphism means an organization of genes in which two alleles are preserved in steady balance because the heterozygote is more robust than the individual homozygote. The discussion has been augmented citing phenomena in malarial and non-malarial environments.