Sickle cell anemia: The selective forces that a population experiences can vary

Question

Sickle cell anemia: The selective forces that a population experiences can vary by context, especially by geographic place. Please answer following BRIEFLY. a) Explain in your own words how natural selection affects the evolution of hemoglobin in humans and how and why the selective pressures differ among human populations. b) For your answer to part a, which are examples of disruptive, stabilizing or directional selection? c) For human populations living in regions of the world without malaria, do you expect the HS allele to eventually go extinct? Explain briefly.

Explanation / Answer

a) The malaria parasites on human population can exert selective pressure this led to the natural selection of erthrocytes.Erythrocytes or RBCs carry the sickle cell hemoglobin gene mutation and highly protected against malaria thus, malaria as an agent of natural selection seemed a better candidate than an infectious disease causing occasional epidemics and it helps to prevent it by giving some resistance to the disease.

Selective pressures differ among human populations by giving the required dosage that a human being can bare and this taken in larger amount.

b) Directional selection is a type of natural selection ,one extreme of the trait distribution experiences selection against it or it favors one extreme phenotype over the mean or another extreme phenotype.

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