Which effect can result from genetic drift in small populations?

Genetic drift is a phenomenon that has a profound impact on small populations due to the random nature of allele frequency changes from one generation to the next. In these small populations, alleles — the different versions of a gene — can experience significant fluctuations purely by chance. This randomness can lead to the complete loss of some alleles, meaning they diminish to a point where they are no longer present in the population. Conversely, other alleles may become fixed, where they reach a frequency of 100% and are the only version remaining in that population.

Because small populations have a limited gene pool, the effects of genetic drift can be particularly pronounced, often leading to a reduction in genetic diversity. This loss can have severe implications for the population's ability to adapt to changing environments, making them more vulnerable to extinction. As a consequence, the statement that alleles can be completely lost or fixed in the population accurately reflects a key outcome of genetic drift in small populations.