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Lecture 5

BIO SCI 94 Lecture Notes - Lecture 5: Genetic Drift, Allele Frequency, Genotype FrequencyPremium


Department
Biological Sciences
Course Code
BIO SCI 94
Professor
Brad Hughes
Lecture
5

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1/16/2019
Lecture 5 -Evolutionary Processes and Patterns
Ecological Selection
Sexual selection contradicts Hardy-Weinberg Principle
One type of natural selection
Ecological Selection-Prefer traits which help animal survive
Different selections may act on an animal at same time which may favor
the same traits
Genetic Drift
Genetic Drift- Due to chance, the population experiences an allele frequency
change
Over time, allele frequencies drift up and down over time
Every population experiences drift every generation
More obvious in small populations
Simulation Studies of Genetic Drift
Mother- ATAH
Father- ATAH
Sperm
Egg
Genotype
First Offspring
AH
AT
AHAH
Second Offspring
AT
AT
ATAT
Third Offspring
AT
AH
AHAT
Fourth Offspring
AH
AH
AHAH
Fifth Offspring
AT
AH
AHAT
Notice: In Genotype column, there are 6 AH and 4 AT. Due to genetic drift, allele
frequency changed.
Computer Simulations
Computer simulate random combinations over time
Simulations show
Genetic Drift effects are greater in small populations
Over time, one allele will drift up or down
Drift can be important in large population given enough time
Key Points about Genetic Drift
Effects are most obvious in small populations
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