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Evolution

Evolution. Hardy-Weinberg Principle. I ntro. Last day we left off talking about populations… Populations geneticists are able to quantify the total number of alleles within a population == this is known as the gene pool

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Evolution

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  1. Evolution Hardy-Weinberg Principle

  2. Intro • Last day we left off talking about populations… • Populations geneticists are able to quantify the total number of alleles within a population ==this is known as the gene pool • They are able to accomplish this by measuring each allele frequency, which is the proportion of gene copies in a population for a given allele • Therefore evolutionary changes in populations can be quantitatively measured by looking for changes in allele frequencies

  3. Example

  4. Hmmm… • In terms of evolution, would the dominant form of a moth wing become more and more common over time? • Do allele frequencies remain constant or change over time? • These questions were answered independently (think Darwin vs. Wallace) by a mathematician named Hardy and physicist named Weinberg== thus Hardy-Weinberg principle

  5. The Principle • Allele frequencies will not change over time (generation-generation) if the following conditions are met: • The population is very large • Mating opportunities are equal • No mutations occur • No migration occurs • All individuals have an equal chance at reproductive success==no natural selection

  6. Equation • The H-W-P is often expressed using the following equation (for a gene with only 2 alleles==A/a): • let p=frequency of A and q=frequency of a, then p+q=1 (p+q)2= 1 p2 + 2pq + q2 = 1, where p2= frequency of AA; 2pq= frequency of Aa; and q2 = frequency of aa

  7. Moth example Note: genotype frequencies will remain the same from generation to generation as long mating is random

  8. Reference Pgs 547-549 Pg 549 PP’s #1-3 Quiz Tomorrow -self quiz -review #1-4, 7, 8, 10, 15

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