What is the founder effect? How can it influence the genetic profile of a population?

The founder effect occurs when a small number of individuals moves away from the main population, populate a new area, and found a new population. Two notable effects on the genetic profile of a founder population can be: decreased genetic variation, and increased occurrence of rare alleles. The founder effect is an extreme example of genetic drift, as the variation in the limited gene pool of this smaller founding population can be very different from -- and is generally much more limited in variation than -- that of the main population. A small selection of individuals cannot carry as much variation as the entire original population. Should rare alleles from the main population be carried along in a founding population, their frequency will likely be much higher in the newly founded population. This is due to the relative frequency of these alleles being higher within the small founding population than it is in that of the original population.