What does the founder effect refer to in genetics?

The founder effect refers to a loss of genetic variation when a small subset of a larger population establishes a new population. This phenomenon occurs because the new population is formed from a limited number of individuals, leading to a restricted gene pool. As a result, certain alleles present in the founders can become more common, while others may be lost entirely. This can have significant implications for the genetic diversity of the new population, potentially making it more susceptible to diseases and reducing its adaptability to environmental changes.

In this context, gaining genetic diversity would be incorrect as the founder effect typically results in reduced variation. Similarly, the suggestion that only the fittest individuals survive relates to natural selection rather than the specific dynamics of population founding. Lastly, a shift in allele frequencies due to geographic isolation pertains more to the concept of genetic drift or speciation, not directly reflecting the scenario of a small group starting a new population. Thus, the key aspect of the founder effect is the initial loss of genetic variation linked to the small number of individuals who begin the new population.