What is the Founder Effect?

• A. Increase in genetic variability due to new mutations.
• B. The reduction in genomic variability occurs when a large group migrates.
• C. The mixture of many populations increases diversity.
• D. The reduction in genomic variability occurs when a small group becomes separated from a larger population.

Answer: (D)

The founder effect is a type of genetic drift that happens when a new population is started by a small number of individuals from a larger population. Because only a tiny slice of the original gene pool is carried into the new group, the new population ends up with reduced genetic variation. The allele frequencies in this founder population can be quite different from the parent population simply by chance, and some alleles present in the original group may be missing entirely in the new one. This is why a small colonizing group leads to less genomic variability in the new population. If a large group had moved, or if many populations mixed, the genetic diversity would be maintained or increased rather than reduced. New mutations can add variation, but they don’t explain the observed reduction in diversity that comes from the founder event.