If the Condition Known as Sickle Cell Anemia Involves a Mutant

question 24

Multiple Choice

If the condition known as sickle cell anemia involves a mutant variant of a gene that can be fatal, why does it have a frequency as high as 20 percent in the gene pool of certain populations?

• A) It is theorized that in areas where the malarial parasite is endemic, the advent of agricultural practices leads to a change in natural selection pressures acting on the genetic traits of these populations.
• B) People bitten by an infected mosquito have a better chance of resisting the malarial parasite if they carry one copy of the mutant variant in addition to the normal hemoglobin variant.
• C) Because the combined effects on a population of more than one disease can be exacerbated by a variety of stressful environmental factors.
• D) Both a and b
• E) None of the above.