Founder effect
The founder effect is a change in genetic variation that occurs when a small group establishes a population with only part of the original gene pool.
Genetic drift: Changes in allele frequencies caused by random sampling across generations, especially in small populations. The founder effect is a form of genetic drift produced by population establishment.
Pennsylvania Dutch: A cultural group descended largely from German-speaking immigrants who settled in Pennsylvania from the seventeenth century onward. Some inherited conditions are unusually frequent in this historically isolated population.
Population genetics: The study of genetic variation within and between populations and how it changes over time. Founder effects are a central process in explaining population-level genetic differences.
Coalescent theory: A mathematical framework that traces sampled gene copies backward to their common ancestors. It links present-day genetic data to the small ancestral groups that founded populations.
Evolution: Heritable changes in populations across generations. Founder effects alter genetic variation and can redirect subsequent evolutionary change.
Allele frequency: The proportion of copies of a gene in a population that carry a particular allele. Founder effects change these proportions when founders carry an unrepresentative sample.
Ellis–van Creveld syndrome: A rare inherited disorder affecting skeletal growth, teeth, nails, and sometimes the heart. Its elevated frequency among some Pennsylvania Amish communities illustrates founder-related enrichment of recessive variants.
Genetic epidemiology: The study of how genetic variation contributes to patterns of disease in populations. Founder effects can make particular disease-associated variants unusually common in a population.
Demographic inference: The reconstruction of population size changes, migration, and splits from genetic or other data. It tests whether observed variation reflects founding, bottlenecks, migration, or later expansion.
Natural selection: A process in which heritable variants affect survival or reproduction, changing their frequencies over generations. Unlike selection, founder-driven frequency shifts arise from sampling chance rather than fitness differences.