1) A gene mutation observed in high frequency in a specific population due to the presence of that gene mutation in a single ancestor or small number of ancestors.

2) The founder effect is the reduction in genetic variation that results when a small subset of a large population is used to establish a new colony. The new population may be very different from the original population, both in terms of its genotypes and phenotypes. In some cases, the founder effect plays a role in the emergence of new species.