Transcript Hardy Weinberg Principle (equilibrium)

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Allele frequencies will remain constant unless one
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If there is no change, there is no evolving.
or more factors cause the frequencies to change.
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Natural selection acts on the range of
phenotypes in a population.
Evolution occurs as a population’s genes and
their frequencies change over time.
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All of the alleles of a population’s genes
together make up a gene pool.
Allele frequency - % of any specific allele in
the gene pool.
Genetic equilibrium – a population in which
the frequency of alleles remains the same
over generations.
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Mutations are one cause of genetic change.
Lethal mutations disappear quickly, but
mutations that cause a useful variation
become part of the gene pool
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Genetic drift – the alteration of allele frequencies by
chance events.
Gene flow – transport of genes into or out of a
population by migrating individuals.
Genetic drift, gene flow, and mutations can greatly
affect small populations.
Natural selection is usually the most significant cause
of changes in any gene pool.
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Some variations increase or decrease an
organism’s chance of survival in an
environment.
Variations are controlled by alleles.
Allelic frequencies in a gene pool will change
due to natural selection of variations.
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If conditions are not met the genetic
equilibrium is disrupted –
*population evolves and changes*
If conditions are met the genetic equilibrium
stays the same–
*population does not evolve*
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Genotype proportions remain constant –
calculated from allele frequencies
P+Q = 1 or 100 percent
(allele frequencies)
P2 + 2PQ + Q2 = 1 or 100 percent
(genotype frequencies)
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P = frequency of the dominant allele in the population
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Q = frequency of the recessive allele in the population
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P2 = percentage of homozygous dominant individuals
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Q2 = percentage of homozygous recessive individuals
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2PQ = percentage of heterozygous individuals
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If 98 out of 200 individuals in a population
express the recessive phenotype, what
percent of the population are
homozygous dominant?