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Lecture 11

BIOL 1001 Lecture Notes - Lecture 11: Zygosity, Chin, Genetic Drift


Department
Biology
Course Code
BIOL 1001
Professor
Tamara Kelly
Lecture
11

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BIO 1001 MECHANISMS OF EVOLUTION FEBRUARY 8H 2017
Four mechanisms give rise to evolution
- Migration
- Natural selection
- Genetic Drift: drift in allele frequencies
o In all population, initial frequency is 0.5 and sometimes it goes to fixation or
loss but it is all due to chance, these alleles do not offer advantage or
disadvantage
- Gene flow (migration)
Two of the major ways we see effect of a drift:
Population bottleneck
: the surviving members of a catastrophic event can have different
allele frequencies than the source population and consequently, the new population
experiences evolution
o Can also be defined as sudden reduction in total number of alleles in
population
o Odds of survival is random therefore no genetic advantage
o Occasionally, famine or rapid environmental change may cause the death
o New population will be dominated by genetic features present in surviving
members
o Does the surviving population have allele frequencies similar to the source
population?
o Loss of alleles and reduced genetic variability
Evidence of population bottlenecks very much reduced genetic
variation in population
Eg. Chickens before settlers were 100 million in Illinois, now there are
<50 due to randomly hunting (no set trait wanted, just random
hunting)
o Does the surviving population have allele frequencies similar to source
population?
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