Genetic Drift & Evolution

1. Genetic Drift& Evolution APES

2. Gene Pools • Genetic Drift is the change in a gene pool due to chance. • There are 2 examples: • Bottleneck effect • Founder effect

3. 1) Bottleneck Effect • Reduce the size of a population randomly • Natural disasters • Ex: fire, earthquake, flood • Results in the loss of genetic variation • Smaller population • Not representative of the original one • Certain alleles may be over or underrepresented

5. 1) Bottleneck Effect: Tay-Sachs • High rate among Eastern European Jews • Attributed to population bottleneck in Middle Ages • Population was dramatically reduced at this time • Individuals who remained alive & reproduced just happened to be ones who carried Tay-Sachs

6. 2) The Founder Effect • When a small population breaks away from a larger one • Colonize a new area • Extreme isolation & intermarriage leads to high frequencies of specific traits

7. Natural Selection • Remember that natural selection is the major mechanism of evolution in any population. • “Survival of the Fittest”

8. Any Questions?