Sickle Cell Anemia Case Study

B1.1 Where do you think you’ll find that the most villagers are dying from sickle-cell anemia? Explain.

Most villagers that are dying from sickle-cell anemia will come from the villagers at the very wet regions where there are many mosquitoes. The simulation shows that the malaria death for very wet regions rate is 0.2, that is the highest number compared to other regions. It is because there are many mosquitos in that area, so that area might be where malaria has long been endemic. Because of that, the villagers in those very wet regions have evolved dozens of chemical as defenses against malaria and the sickle cell is one of them (anti-malarial). Natural selection acts so that people with sickle cell allele are more common in those very wet regions as they survive and reproduce better in the environment where malaria is endemic, especially those people with heterozygous sickle cell allele (HbA/HbS) as it acts as ‘shield’ that protect them from dying from malarial disease and also sickle cell disease. However, those who have sickle cell allele especially the homozygous for the

sickle cell allele have high chance to be dying with sickle cell anemia. People with homozygous HbS protected against malaria, but not sickle cell anemia, that’s why they died from sickle cell anemia but not malaria and that is why we can see lots of people dying from the sickle-cell anemia in this region.

B1.2 Do you think the sickle-cell allele will disappear in any of your runs for the different regions?

Explain.

Yes, the sickle cell allele will disappear but only at the dry area where there are no mosquitoes. It is because, if we applying the natural selection theory, people with sickle cell will not have any advantage at environment that do not have or have very little cases of malaria, like the dry area that have no mosquitoes. People with sickle cell anemia at the dry area will die from the sickle cell disease, as the antimalarial properties of the sickle cell is not an advantage at the dry environment, including those that are sickle cell disease carrier. So, as the time goes by, the population with sickle cell anemia will die out and disappears, because those that did not have sickle cell allele will survive and reproduce better compared to those who have the sickle cell

allele.