Final answer:
Recessive, deleterious mutations that arise repeatedly are usually eliminated through natural selection, although they may be kept in the gene pool by carriers. Highly beneficial alleles, on the other hand, may become fixed in the population.
Step-by-step explanation:
The fate of a recessive, deleterious mutation that arises repeatedly depends on natural selection. In most cases, such mutations will be eliminated from the population through natural selection. Natural selection acts on the phenotype, so if a recessive allele causes death in a homozygous individual, it will not cause death in a heterozygous individual. These heterozygous individuals will then act as carriers of the allele, keeping it in the gene pool. However, highly beneficial alleles may become fixed in the population over time.