How does sickle-cell allele relate to natural selection?

How does sickle-cell allele relate to natural selection?

Heterozygotes (AS) with the sickle-cell allele are resistant to malaria. Therefore, they are more likely to survive and reproduce. This keeps the S allele in the gene pool….Sickle Cell and Natural Selection.

Genotype Phenotype Fitness
AA 100% normal hemoglobin Somewhat reduced fitness because of no resistance to malaria

Which the evolutionary forces apply to the persistence of the sickle-cell allele?

An evolutionary force, called balancing selection, appears to be responsible for maintaining defects in our DNA associated with diseases, such as sickle cell anemia, because the mutation’s damaging effects might be offset — in a biological way of thinking — by its potential benefits.

Is sickle-cell An example of stabilizing selection?

Stabilizing selection – In this type the population stabilizes on a single non-extreme trait. It is the most common type of natural selection. It results in the decrease of population’s genetic variation. This type balances the two traits as in sickle cell anaemia which has two alleles.

How does disease affect natural selection?

From an evolutionary perspective, infectious diseases have probably been the primary agent of natural selection over the past 5000 years, eliminating human hosts who were more susceptible to disease and sparing those who were more resistant.

How does the sickle cell allele protect against malaria?

The sickle cells have membranes, stretched by their unusual shape, that become porous and leak nutrients that the parasites need to survive and the faulty cells eventually get eliminated quite fast by the organisms, destroying the parasite along the way.

What process can help explain the maintenance of the sickle-cell allele in these circumstances?

c. A likely explanation for the maintenance of the sickle-cell gene in Africa is that it confers an advantage to heterozygotes by increasing their resistance to malaria. Such overdominant selection results in a stable equilibrium.

Is disease a form of natural selection?

Diseases are thought to persist in human populations primarily because of a balance between mutation, genetic drift, and natural selection, with alleles that contribute to disease introduced by mutation, governed in part by random genetic drift, but eventually eliminated from the population by purifying selection 5, 7.