Download Notes 9.4 – DISRUPTING HWE EQUILIBRIUM

Science Starter #5 – 2/28/17
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
What are the five conditions that need to be met
for Hardy-Weinberg equilibrium? What does that
mean for the population?
TAKE OUT YOUR HWE FLIP
Notes 9.4 –
DISRUPTING HWE
EQUILIBRIUM
Ch. 16-2 pp. 321-325
Hardy-Weinberg Genetic Equilibrium
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Evolution: change in population’s genetic material
(alleles) over time
Genotype frequencies stay the same over time as long
as certain conditions are met:
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Very large (infinite) populations
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No gene flow
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emigration (exit) or immigration (in)
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No mutations
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Random mating
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No natural selection
Conditions to disrupt HWE
1. Mutation
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Produces and introduces new alleles in a population
 Ex.
Conditions to disrupt HWE
2. Gene Flow
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Gene Flow- Movement of individuals in or out of a
population
 Immigration
 Ex.
– In and Emigration – Exit
Conditions to disrupt HWE
3. Genetic Drift
Genetic Drift - The amount of an allele changes due
to random events
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Affects small populations mostly
Lose alleles if not enough to mate or a catastrophe occurs
Ex.
Conditions to disrupt HWE
4. Non-random mating
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Sexual Selection - Choose mates based on specific
traits and those traits increase in the population
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Amplifies certain traits and reduces others through sexual
selection
Conditions to disrupt HWE
5. Natural Selection (3 Types)
Organisms best suited to their environment live to
reproduce and pass on their genes
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Acts on a phenotype
Three types of selection
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Directional, stabilizing, disruptive