Download Hardy-Weinberg Equilibrium

Hardy-Weinberg Equilibrium
Honors Biology
Is evolution occurring right now?
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How might a scientist
tell if evolution is
occurring within a
population?
Hardy-Weinberg Theorem
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Biologists use models to study populations
Hardy-Weinberg equilibrium is a type of
model
■
Provides a framework for understanding how
populations evolve
The Hardy-Weinberg Theorem
Microevolution
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■ changes
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in gene pool over time
Gene pool
■ combination
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of all alleles for a
trait in a population
If allele frequencies change over
time, the population is evolving
If allele frequencies are stable
(don’t change), the population is at
equilibrium and no evolution is
occurring
Hardy-Weinberg Equilibrium Conditions
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Genotype frequencies
stay the same (no
microevolution) if all
5 conditions are met:
1.
2.
3.
4.
5.
No natural
selection
No Mutations
Isolation from
other populations
Very large
population size
Random Mating
•Meeting
all 5
conditions is nearly
impossible
Hardy-Weinberg Equation
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p+q=1
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p2
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p = frequency of dominant allele
q = frequency of recessive allele
+ 2pq + q2 = 1
p2 = frequency of homozygous dominant genotype
(AA)
2pq = frequency of heterozygous genotype (Aa)
q2 = frequency of homozygous recessive genotype
(aa)
Solve this story problem
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In pigs, the allele for black skin is
recessive to pink skin.
B = pink; b = black
Calculate q2 for the illustration shown
below.
q2 = 0.25 (4/16)
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Find q.
■
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Find p.
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q = 0.5
p = 0.5
Find 2pq.
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2pq = 0.5
This means 50% of the pink pigs are
heterozygous.
Solve this story problem
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In a certain flock of sheep, 4 percent of
the population has black wool and 96
percent has white wool.
If black wool is a recessive trait:
■
■
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What percentage of the population is
homozygous black? (q2)
What percentage of the population is
heterozygous for this trait? (2pq)
What percentage of the population is
homozygous white? (p2)
Extra Help!
•
Bozeman Biology Solving Hardy Weinberg
Problems