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 Sickle Cell Anemia

Credit: Wikimedia Commons

Sickle cell disease is a genetic disorder that causes red blood cells to take on a deformed sickle shape instead of their normal disk shape, leading to poor circulation, pain, and anemia (low blood cell count). Sickle cell disease is more common in Africa, partly because it gives resistance to malaria, a mosquito-carried disease that targets blood cells. 


What Is the Frequency of the Mutation (rs334) that Causes Sickle Cell Disease in Africa?


1. Go to

2. In the search box, type rs334. This is the ID of the primary mutation that causes sickle cell disease. Hit "Go" to search.

3. In the search results list, click the link for rs334.

4. This page gives lots of information about this mutation. Under "Explore this variation," click the button that says "Population genetics" (near the middle of the page).

5. You should see a series of pie charts. Hover your mouse over each one to see which population it corresponds to. The pie charts tell you the frequency of different nucleotides at this position. In this case, the normal nucleotide is T, and the mutant nucleotide is A.

6. Write down the percentage of the A nucleotide in the African population. This is how frequent this mutation was in the people studied by the 1000 Genomes Project (it's only a small sample of the people in Africa!). Note that because sickle cell disease is a recessive condition, only people with two copies of the A mutation will actually have the disease. However, even having just one copy of the mutation still gives resistance to malaria!


Additional Resources

Sickle cell trait and malaria protection

About the 1000 Genomes Project