I think the correct answer would be the last option. People with one sickle cell allele are not likely to get malaria. This would be an example of genetic drift. It is one of the mechanism of evolution which involves the change in the frequency of an allele in a certain population due to the random sampling of the organisms. It is when a certain trait is being spread by chance rather by natural selection. Sickle cell is classified as an autosomal recessive disease that is caused by hemoglobin. It is a disease that is inherited depending on how the alleles are received. So, it can be inherited by chance.
As the race begins, all of your physiological support systems - the musculoskeletal, cardiovascular, respiratory, digestive, immune, nervous, ...
Nucleus is the answer your looking for I'm positive its correct. If you have anymore questions feel free to post them.
Answer:
Small populations
In small population sizes, inbreeding, or mating between individuals with similar genetic makeup, is more likely to occur, thus perpetuating more common alleles to the point of fixation, thus decreasing genetic diversity.
Explanation: