Which of the following are TRUE with regard to Sickle Cell Anemia and/or Sickle Cell Trait in modern human populations living near the equator? (multiple answers possible)

Question

Which of the following are TRUE with regard to Sickle Cell Anemia and/or Sickle Cell Trait in modern human populations living near the equator?  (multiple answers possible)

BlackTom AI · Accepted Answer

The question asks us to evaluate multiple statements about Sickle Cell Anemia and Sickle Cell Trait in equatorial populations, with malaria as a key selective pressure.
Option 1: 'Everyone who has the sickle cell gene, either in the full disorder or as a carrier, dies before reaching reproductive age, thus there is no adaptive advantage.' This is incorrect. Sickle Cell Trait (heterozygotes) provides a partial protection against malaria and many carriers survive to reproduce; the full disease (Sickle Cell Anemia) can reduce lifespan but is not universal in causing early death and does not preclude reproduction in many cases, especially in regions with high malaria burden where carriers are favored. The blanket claim ignores heterozygote advantage and population-level dynamics.
Option 2: 'There is no adaptive advantage in these areas to having Sickle Cell Anemia or normal hemoglobin.' This is false. In malaria-endemic equatorial regions, individuals with the Sickle Cell Trait have a higher survival rate than those with normal hemoglobin when exposed to malaria, illustrating an adaptive advantage for heterozygotes. The claim ignores the well-documented heterozygote advantage and the malaria selection pressure.
Option 3: 'There is an adaptive advantage to having Sickle Cell Trait in areas where young people regularly die from malaria.' This is true. The heterozygous state confers partial resistance to malaria, reducing the likelihood of severe disease and death in carriers, which increases reproductive success in high-malaria regions.
Option 4: 'The prevalence of Sickle Cell Trait in equatorial areas is one piece of evidence that natural selection is currently at work in modern human populations.' This is true as well. The geographic distribution and higher frequency of the trait in malaria-endemic regions fit a pattern of natural selection in action, consistent with ongoing evolutionary processes in humans.
Option 5: 'Sickle Cell Trait provides natural resistance to malaria but is not good evidence of natural selection at work in humans.' This is misleading. While trait-associated resistance is the mechanism, the pattern of allele frequency variation across populations provides strong evidence of selection acting on humans over time, so it is good evidence of natural selection at work.
Option 6: 'Those with normal hemoglobin are more resistant to the malarial parasite, whereas those with Sickle Cell Anemia and Sickle Cell trait have little to no resistance.' This is inaccurate. Normal hemoglobin individuals are more susceptible to malaria than Sickle Cell Trait carriers, who enjoy some protective effect; individuals with Sickle Cell Anemia generally have compromised health, but the statement wrongly claims resistance is higher in normals and overstates the risk for carriers.

ANTH101 #73038 Online (Fall 2025) Exam 2

Which of the following are TRUE with regard to Sickle Cell Anemia and/or Sickle Cell Trait in modern human populations living near the equator? (multiple answers possible)

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