What is the definition of genetic drift?

The definition of genetic drift is accurately described as a change in allele frequency due to random sampling effects. This process is particularly influential in small populations where chance events can lead to significant shifts in the genetic makeup from one generation to the next. For example, if a few individuals randomly reproduce, the alleles they carry may not represent the allele frequencies of the entire population. This random fluctuation can result in certain alleles becoming more or less common purely by chance, which can have a profound impact on the population's genetic diversity over time.

In contrast to other options, natural selection is a systematic process that alters allele frequencies based on advantageous traits rather than at random, which characterizes genetic drift. Mutation leads to new alleles but does not directly alter existing allele frequencies through random processes. Lastly, the notion of consistent alteration implies a predictable change, which does not reflect the random nature of genetic drift where shifts can be unpredictable. Thus, option C accurately encapsulates the random influence of genetic drift on allele frequencies.