Question

sickle cell: natural selection in humans

1. these maps show the sickle cell allele frequency in newborns in 2010 and the regions of the world where malaria is or was common until relatively recently.

using the maps, which statement supports the claim that rates of malaria and sickle cell are related?
a. regions with a higher sickle cell allele frequency in newborns tend to have historically high levels of malaria.
b. most of the areas with a lower sickle cell allele frequency in newborns have historically high levels of malaria.
c. most of the areas with a higher sickle cell allele frequency in newborns historically use insecticides to control mosquitoes.

1. which statement about having one sickle cell allele is correct?

a. a sickle cell allele is a disadvantage to anyone who inherits it.
b. a sickle cell allele is beneficial to anyone who inherits it.
c. it is beneficial in certain environments and not in others.

1. after watching the film, two students make claims about the connection between malaria and sickle cell trait.

• claim 1: a high incidence of malaria causes the mutations that result in sickle cell trait.
• claim 2: even though people living in these areas have a higher frequency of the sickle cell allele, malaria does not cause the mutations.

which of the following statements is most accurate and provides a valid argument for supporting the associated claim?
a. argument for claim 1: the presence of malaria parasites in an individual’s red blood cells triggers sickle cell alleles to form.
b. argument for claim 1: chemicals in the saliva of the mosquitoes stimulate sickle cell alleles in red blood cells.
c. argument for claim 2: over many generations, mosquitoes become resistant to sickle cell alleles present in heterozygous individuals.
d. argument for claim 2: the sickle cell alleles are present when an individual is born and provide some protection against malaria.
www.biointeractive.org
published january 2025
page 3 of 4

Explanation:

1. By observing the maps, regions with higher sickle - cell allele frequency in newborns align with areas of historically high malaria prevalence, which shows a relationship between the two.
2. Having one sickle - cell allele (heterozygous condition) provides resistance to malaria in malaria - endemic areas, but in non - malaria areas, it may not have such an advantage and can cause some health issues in the long run. So it is beneficial in certain environments and not in others.
3. Sickle - cell alleles are genetic mutations that are present at birth. They offer some protection against malaria, but malaria does not cause the mutations.

Answer:

1. a. Regions with a higher sickle cell allele frequency in newborns tend to have historically high levels of malaria.
2. c. It is beneficial in certain environments and not in others.
3. d. Argument for Claim 2: The sickle cell alleles are present when an individual is born and provide some protection against malaria.