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How do we know if a population is evolving?

How do we know if a population is evolving?. Hardy Weinberg Equilibrium. When is a population not evolving?. How do we know if a gene pool has changed? The Hardy-Weinberg Principle can help answer these questions. How can a population’s genes change over time?.

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How do we know if a population is evolving?

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  1. How do we know if a population is evolving? Hardy Weinberg Equilibrium

  2. When is a population not evolving? • How do we know if a gene pool has changed? • The Hardy-Weinberg Principle can help answer these questions

  3. How can a population’s genes change over time? • All of the alleles of a population’s genes together make up a genepool • Allele frequency - percent of any specific allele in the gene pool • Genetic equilibrium – a population in which the frequency of alleles remains the same over generations

  4. The Hardy-Weinberg Principle states: • Genetic equilibrium will be reached if the frequency of alleles remains stable generation after generation • Genetic equilibrium = no evolution occurring

  5. Hardy-Weinberg Principle • Conditions necessary for genetic equilibrium are: • No mutation occurs • Immigration and emigration do not occur (population is isolated from other populations) - no gene flow. • Population is very large • Mating is totally random • All individuals survive and reproduce equally (no natural selection)

  6. Hardy-Weinberg Principle • It is virtually impossible to meet these conditions • Allelic frequencies do change in populations, therefore evolution occurs • The main application of this principle is calculating allele and genotype frequencies in a population

  7. In a population, the sum frequency of alleles will equal 1 • This can be expressed as: • p + q = 1 • Where: • p = frequency of the dominantallele • q = frequency of recessiveallele

  8. Hardy-Weinberg Equationp2 + 2pq + q2 = 1 • Where: • p2 = frequency of individuals homozygousdominant • 2pq =frequency of heterozygous individuals • q2 = frequency of individuals homozygousrecessive

  9. 4 simple rules for calculating equations: • Find what q2 and q are first • They can be determined with the information given to you in a problem. The q2 population are the homozygous recessive individuals. Once you solve for q2, take the square root to find q. • Once you find what q is, you subtract that number from 1 • p + q = 1. That will give you p, or the number of dominant alleles in a population • Square the p numberto solve for p2 • This will give you the number of homozygous dominant individuals in a population. • Now that we have p2, p, q2, and q, plug those numbers into the 2pq • Check your work by plugging into each equation and see if they equal 1

  10. Question • If 98 out of 200 individuals in a population express the recessive phenotype, what percent of the population are homozygous dominant? (Recessive phenotype = homozygous genotype) p + q = 1 p2 + 2pq + q2 = 1 q2 = = 0.49 q = p = p2 = 2pq =

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