Question

sickle cell: natural selection in humans

1. harmful alleles are typically removed from a population by natural selection. using this information and knowledge from the film, the best explanation for why the sickle cell allele (s) persists in the human population is that:

a. individuals with the unmutated ss genotype do not need the s allele in regions where there is no malaria.
b. genetic engineering has made it possible to insert the s allele into the dna of an individual with the ss genotype to protect them from mosquitoes.
c. individuals with the ss genotype live longer and have more children because they have an increased chance of surviving malaria compared to individuals with the ss genotype.
d. in regions where malaria is common, individuals with the ss genotype are more likely to survive and pass on their genes (including the mutated s allele) than individuals with the ss genotype.

Explanation:

The sickle - cell allele persists because in malaria - endemic regions, heterozygous individuals (Ss genotype) have a survival advantage. They are more resistant to malaria compared to homozygous normal (SS) individuals, allowing them to survive and pass on their genes, including the sickle - cell allele.

Answer:

d. In regions where malaria is common, individuals with the Ss genotype are more likely to survive and pass on their genes (including the mutated s allele) than individuals with the SS genotype.