Question

hhmi biointeractive
lesson 4: why is there a higher frequency of sickle cell disease in some parts of the world?
sickle cell disease storyline
student handout
part 2: does the relationship between sickle cell disease and malaria occur in other parts of the world?
watch clip 4 and observe figure 2.
figure 2. historical prevalence of malaria around the world, indicated by different colors.

1. describe any patterns you notice in figure 2.
2. based on figure 2, identify the parts of the world where you expect there to be a high frequency of the sickle cell (s) allele.

Explanation:

For question 2: Observe the map's color gradient to spot malaria prevalence trends. High malaria prevalence is concentrated in tropical/subtropical regions, while temperate regions (like most of North America, Europe, southern South America, Australia) are malaria-free or have low prevalence.
For question 3: The sickle cell (s) allele has a high frequency in areas with high malaria prevalence, due to the heterozygote advantage (carriers of the allele have increased resistance to malaria).

Answer:

1. High historical malaria prevalence is concentrated in tropical and subtropical regions, including most of sub-Saharan Africa, parts of South Asia, Southeast Asia, and northern South America. Temperate regions such as most of North America, Europe, southern South America, and Australia are mostly malaria-free or have low malaria prevalence.
2. High frequency of the sickle cell (s) allele is expected in sub-Saharan Africa, parts of South Asia (like India), Southeast Asia, and northern South America (regions with high historical malaria prevalence shown in Figure 2).