This document discusses genetic drift, which is changes in allele frequencies in a population due to chance events rather than natural selection. Genetic drift is more likely to have large effects in small populations and can cause increases in neutral, beneficial, or detrimental traits randomly. Two types of genetic drift are founder effects, which occur when a new population is founded by a small number of colonists, and population bottlenecks, when a population is drastically reduced in size, such as by a natural disaster. Examples are provided of each type.

1. Notes: Genetic Drift (pg 10)

2. Notes: Genetic Drift (pg 10)
• Genetic Drift = Change in allele frequencies in
a population due to chance events

3. Notes: Genetic Drift (pg 10)
• Genetic Drift = Change in allele frequencies in
a population due to chance events
• More likely to have a large effect in small
populations

4. Notes: Genetic Drift (pg 10)
• Genetic Drift = Change in allele frequencies in
a population due to chance events
• More likely to have a large effect in small
populations
• Unlike natural selection, which favors
beneficial traits, genetic drift is random and
can cause an increase in traits that are
beneficial, detrimental, or neutral

5. Types of Genetic Drift
1. Founder effect: Changes in gene frequency
due to colonization of a new area by a limited
number of individuals

6. Types of Genetic Drift
1. Founder effect: Changes in gene frequency
due to colonization of a new area by a limited
number of individuals
Example: British colony on Tristan da Cunha
island founded by 15 people. 1 colonist
carried an allele for a type of blindness.
Today, 2% of individuals on the island are
blind, compared to <0.01% in the general
population

7. 2. Population bottleneck: Change in gene
frequency caused by a drastic reduction in the
size of a population, usually due to a natural
disaster or hunting

8. 2. Population bottleneck: Change in gene
frequency caused by a drastic reduction in the
size of a population, usually due to a natural
disaster or hunting
Example: Cheetahs. 2 Bottlenecks: 10,000 years
ago (ice age) and 1800’s (hunting). Now
cheetahs are very similar genetically, leading
to problems associated with inbreeding

9. Output activity (pg 11)
Imagine that a massive earthquake kills all
humans on Earth except for President Obama
and Vice President Biden and their families
(they were safely aboard Air Force One).
These people will now repopulate the Earth

10. Output activity (pg 11)
Imagine that a massive earthquake kills all
humans on Earth except for President Obama
and Vice President Biden and their families
(they were safely aboard air force one). These
people will now repopulate the Earth
1. Are these people a representative sample of
human genetic diversity? Explain.
2. List at least 5 genetic traits that would be lost
due to this population bottleneck