Transcript Population Genetics - Building Directory

Population Genetics
Modern Synthesis of Evolution
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Integrates discoveries and ideas from many
different fields, including paleontology,
taxonomy, biogeography, and population
genetics
Emphasizes
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Populations evolve, not individuals
Natural selection is the most important mechanism
of evolution
Gradualism – large changes evolve as an
accumulation of small changes over a long time
Population
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A population is a group
of organisms of the
same species that live
in a certain area
A gene pool is
composed of all the
genes in a population
The Hardy-Weinberg Theorem
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It states:
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“The frequency of alleles and genotypes in a
population’s gene pool will remain constant over
the generations unless acted upon by agents
other than sexual recombination”
WHAT??
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The number of alleles and genotypes is not going
to change in a given population is not going to
change (unless the population is NOT in
equilibrium)
5 Conditions Required for
Hardy-Weinberg Equilibrium
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Very large population size
Isolation from other populations
No net mutations
Random mating
No natural selection
The Hardy-Weinberg
Equations
p2 + 2 pq + q2 = 1
p+q=1
p=frequency of dominant allele (A)
q=frequency of recessive allele (a)
p2=frequency of AA
q2= frequency of aa
2pq=frequency of Aa
The Hardy-Weinberg Theorem
How is it helpful?
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Although the Hardy-Weinberg theorem
describes a gene pool in equilibrium (ie. one
that is NOT evolving), it can help us
understand that evolution DOES occur
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If p and q change over time, then the
population is evolving. We can gauge how
quickly the population is evolving by how
much p & q change over time.