Download Genetic Drift

Genetic Drift
& Evolution
APES
Gene Pools
Genetic Drift is the change in a gene pool
due to chance.
There are 2 examples:
Bottleneck effect
Founder effect
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
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
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
Natural Selection
Remember that natural selection is the
major mechanism of evolution in any
population.
“Survival of the Fittest”
Any Questions?