Introducing
Your new presentation assistant.
Refine, enhance, and tailor your content, source relevant images, and edit visuals quicker than ever before.
Trending searches
Sickle Cell Anemia and Malaria
5
Sickle Cell Anemia and Microevolution
Kayla Andree
5/11/2022
Sickle Cell Anemia
What is Sickle Cell Anemia?
Normal blood cells are round and flexible and carry proteins called hemoglobin that carry oxygen throughout the body. In people with Sickle Cell Anemia, there is a mutation in the hemoglobin that causes the cell to form a sickled and less flexible blood cell shape. The crescent-shaped blood cells can cause blockages that stop the normal red blood cells from carrying oxygen to other cells. This leads to Sickle Cell Crisis which causes pain in the body. Sickle cell can be life threatening, however, it can also protect the body from another life threatening disease: Malaria.
(Fuseschool, 2022)
Malaria
Malaria
Malaria is caused by a parasite that is carried by mosquitoes. When the parasite enters a normal blood cell it reproduces until it bursts to spread to other blood cells. When malaria enters sickled cells, the blood cell immediately bursts, which ends the parasitic lifecycle and effectively stops the disease from spreading in the body.
(Fuseschool, 2022)
Natural Selection
People that carry the mutated alleles for sickle cell live in areas in which malaria is very common, such as Africa and parts of Asia and South America.Having the sickle cell trait protects against malaria which enables the person to grow to reproduce, making sickle cell a favorable trait in areas with high percentages of malaria.
Heredity
Heredity
Sickle cell anemia is passed by the combination of alleles in parents who also carry the sickle cell gene mutation. Sickle cell is Codominant, meaning a person must carry two copies of the mutated allele to have the sickle cell disease or 1 mutated allele to have some sickled cells, but not as many as a person with sickle cell anemia. To predict possible genotypes of offspring of parents with the sickle cell allele we use punnett squares.
Parent Genotype Example
If the Parents were both carriers of the Sickle Cell allele, they would both be heterozygous SA. This punnett square shows the possible genotypes of their offspring.
S- Sickled cells A- Normal Cells
Parent Genotype
SS Genotype
Sickle Cell Phenotype
SS Genotype
Sickle Cell Phenotype
The offspring with this genotype will have sickle cell anemia and may experience sickle cell crisis. There is a 25% chance that the offspring of the two carrier parents will have sickle cell anemia.
( Fuseschool, 2022)
25%
SA Genotype
Carrier Phenotype
SA Genotype
Carrier Phenotype
People with heterozygous genotype SA have 50% mutated blood cells and are called carriers. Carriers are the most protected from Malaria, because they have sickled cells to protect from the parasite, but not enough to cause blockages. There is a 50% chance that the offspring of the two carrier parents will also be a carrier.
( Fuseschool, 2022)
50%
AA Genotype
Normal Phenotype
AA Genotype
Normal Phenotype
Offspring with this genotype will not have sickle cell, but they are susceptible to Malaria. There is a 25% chance that the offspring of the two carrier parents will have normal blood cells.
( Fuseschool, 2022)
25%
Sickle Cell & Human Evolution
Human Evolution
The mutated sickle cell allele became favorable in environments where malaria is common. When people with the SA genotype encounter malaria they survive, allowing them to mature to have offspring of their own. This resulted in the mutated sickle cell allele becoming more common in the gene pool as a favorable trait. Now that globalization has occurred, people with the sickle cell trait may no longer be in regions where malaria is common, making the trait seem like an unfavorable disease. This however is not true, as the sickle cell trait is a product of the microevolution of the allele that causes sickle cell. Because microevolution occurred in this allele, the sickle cell allele is not in Hardy Weinberg Equilibrium. Any future change in allelic frequencies will mean that there is not HW equilibrium of the gene.
(The Making of the Fittest, n.d.)
Citations :
Citations
Sickle cell anaemia | genetics | biology | fuseschool. (2022, January 14). https://www.youtube.com/watch?v=5cBpNE-k3TQ
The making of the fittest: Natural selection in humans. (n.d.). HHMI BioInteractive. Retrieved May 11, 2022, from https://www.biointeractive.org/classroom-resources/making-fittest-natural-selection-humans
Wadman, M. (2011). Sickle-cell mystery solved. Nature. https://doi.org/10.1038/nature.2011.9342