Final answer:
Genetic drift and population bottlenecks can lead to the loss of rare alleles in a population.
Step-by-step explanation:
Genetic drift is a process that can cause changes in allele frequencies within a population due to chance events. If alleles were already rare prior to genetic drift and a population bottleneck, there is a higher likelihood that they may be lost entirely from the population. This is because in small populations, chance events can have a greater impact on allele frequencies. For example, if a natural disaster reduces the population size, rare alleles may be disproportionately lost due to the random sampling of alleles in the survivors.