Final answer:
The eventual fate of a new beneficial allele in an infinite population is that it will reach fixation regardless of whether it is dominant or recessive. This outcome is the result of natural selection favoring the allele until it is the only variant present in the gene pool.
Step-by-step explanation:
The correct answer to the question about the eventual fate of a new beneficial allele in an infinite population is c) Since it is advantageous, it will reach fixation regardless of whether it is dominant or recessive. When a new beneficial allele arises, natural selection acts on it, increasing its frequency in the population. Over time, if the allele continues to provide a survival or reproductive advantage, it will become more and more common. This process occurs irrespective of whether the allele is dominant or recessive. Yet, a dominant allele might increase in frequency more quickly because its advantage is expressed even when only one copy is present in the genotype.
According to the Hardy-Weinberg principle, allele frequencies in a population will remain constant unless evolutionary forces such as natural selection, mutation, genetic drift, and migration act upon them. In the case of a beneficial allele, natural selection is the evolutionary force that drives it towards fixation. A fixed allele is one that is the only variant present in the population, and thus every individual will be homozygous for this allele.
Examples of this process can be observed in natural populations, such as the spread of antibiotic resistance in bacteria or lactose tolerance in human populations where dairy farming is prevalent. These traits conferred a significant advantage, increasing the carrier's survival or reproduction rates, leading to the fixation of these beneficial alleles in their respective gene pools.