Final answer:
Mutation is the process that can create new alleles within a population, whereas natural selection, sexual reproduction, and genetic drift can alter the distribution and frequency of these alleles but do not create new ones.
Step-by-step explanation:
The process that can create new alleles is mutation. A mutation is a change in the DNA sequence that can introduce new genetic variations into a population. While natural selection, sexual reproduction, and genetic drift all play roles in the evolution and distribution of these alleles, they do not create new alleles. Rather, natural selection and genetic drift can alter allele frequencies within the gene pool, and sexual reproduction can shuffle existing alleles to produce new combinations in the offspring.
For instance, if a rabbit population has two alleles for fur color and a mutation occurs in one of them, a third allele may emerge, changing the gene pool. Such introduction of new alleles through mutation can lead to changes in allele frequencies due to genetic drift. This is because the effects of chance may cause some individuals, regardless of their genetic makeup, to leave more offspring than others. Nonetheless, the only mechanism that actually creates new alleles is mutation.