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**Hardy-Weinberg Equilibrium**

Honors Biology

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**Is evolution occurring right now?**

How might a scientist tell if evolution is occurring within a population?

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**Hardy-Weinberg Equilibrium**

Biologists use models to study populations Hardy-Weinberg equilibrium is a type of model Provides a framework for understanding how populations evolve

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**Hardy-Weinberg Equilibrium Conditions**

Genotype frequencies stay the same (no microevolution) if all 5 conditions are met: Very large population size Isolation from other populations No Mutations Random Mating No natural selection

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**The Hardy-Weinberg Equation**

Uses frequencies of alleles in a population’s gene pool to determine if (micro)evolution is occurring If allele frequencies change over time, the population is evolving If allele frequencies are stable, the population is at equilibrium

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**Hardy-Weinberg Equation**

p + q = 1 p = frequency of dominant allele q = frequency of recessive allele p2 + 2pq + q2 = 1 p2 = frequency of homozygous dominant genotype (AA) 2pq = frequency of heterozygous genotype (Aa) q2 = frequency of homozygous recessive genotype (aa)

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**Solve this story problem**

In pigs, the allele for black coat is recessive to pink coats. B = pink; b = black Calculate q2 for the illustration shown below. q2 = 0.25 (4/16)

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**Find q. Find p. Find 2pq. q = 0.5 p = 0.5 2pq = 0.5**

This means 50% of the pink pigs are heterozygous.

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**Solve this story problem**

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: 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)

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