Natural Selection in Humans

There are now several effective antimalaria drugs that can treat people who have malaria or prevent them from getting the disease altogether. Predict what will happen to the frequency of the sickle cell allele as these drugs become more more widely used. Support your answer with at least one piece of evidence from the film.

As malaria becomes less deadly, selection for a genetic mutation that protects individuals from the disease decreases. As a result, the frequency of the sickle cell allele will likely decrease.

Is the following statement true or false? "Malaria caused the sickle cell allele to appear." Justify your answer in one or two sentences.

False; the sickle cell allele arose randomly. Malaria provided the selective pressure for the allele to increase in frequency in some populations.

Consider the statement: "Sickle cell disease is a(n) _____disease.". Which of the following terms could fill in the blank to make the statement true? Write "yes" or "No" next to each possible response. There may be more than one correct answer.

Genetic: Yes Infectious: No Potentially Lethal: Yes Inherited: Yes

Consider the statement: "An individual with two normal copies of the hemoglobin gene is said to be____." which of the following terms could fill in the blank to make the statement true? Write "Yes" or "No" next to each possible response. There may be more than one correct answer. (Note that a "locus" is a location on a chromosome.)

Homozygous at the hemoglobin locus: Yes Susceptible to malaria: Yes Heterozygous at the hemoglobin locus: No An identical twin: No

If sickle cell disease were caused by only one copy of the sickle cell allele, do you except the frequency of the sickle cell allele to increase, decrease, or remain the same in places where there is a high incidence of malaria? Explain your answer in two or three sentence.

Sickle cell disease can be deadly; as a result, there is a selection against this phenotype. If only one sickle cell allele were to cause the disease, individuals heterozygous for the sickle cell allele would have no selective advantage over individuals homozygous for the sickle cell allele. as a result, the frequency of the sickle cell allele would be lower.

In three to five sentences, explain why sickle cell disease became so prevalent in certain East African populations.

The sickle cell allele is protective against malaria - even when the allele is in the heterozygous state. Malaria is prevalent in the lowlands of East Africa, and so the sickle cell became common. This is because it provided protection against malaria. As a result, sickle cell disease (individuals homozygous for the sickle cell allele) also became common.

At the beginning of the film, you were introduced to Davaun and Skyy Cooper, who both have sickle cell disease. Which of the following must be true about their parent?

B. Both parents have at least one copy of of the sickle cell allele.

Due to climate change, the range of malaria is expected to spread to areas where it was previously not a problem. Given this piece of evidence, predict what will happen to the frequency of the sickle cell allele in areas where malaria is introduced.

Because the sickle cell allele provides some resistance to malaria, the frequency of the allele should increase if the prevalence of malaria increases.

Consider the statement: "Malaria is a(n)______ disease." which of the following terms could fill in the blank to make the statement true? Write "Yes" or "No" next to each possible response. There may be more than one correct answer.

Genetic: Yes Infectious: Yes Potentially lethal: Yes Inherited: No

How does the HbS allele frequency relate to malaria incident in children in European and African populations compared to children in Asian populations?

In Europe and Africa, when there is a high frequency of the malaria parasite, there is a high frequency of the sickle cell allele. In Asia, the frequency of the sickle cell allele is very low, regardless of the frequency of malaria parasites present.

Provide a hypothesis that explains the findings in the Asian population.

The Sickle cell allele never arose or was never introduced to this population.

Provide explanation, based on what you learned from the film, for the trends observed in the European and African populations.

The scientists observed an increased frequency of the HbS allele in regions with high incidences of malaria. This is because people with the sickle cell allele have a selective advantage increase.