Population Genetics

Population Genetics - Review Evolution occurs by: Acquired...

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Review Evolution occurs by: Acquired characteristics (Lamarck) Mutation (DeVries ) Today’s view Mutation provides the variability – new alleles Sexual and genetic recombination (cross over) provide variability by reshuffling existing alleles Natural selection acts on the alleles present in the population causing shifts in their frequency of occurrence
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Review (cont) Acquired characteristics cannot be passed on via DNA to the next generation in sexual reproducing organisms
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Population Genetics This is the study of change in the gene frequency in the population through time . Gene pool = the number of alleles present in the population Gene frequency and genotype frequency remain constant in the population if there is:
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Population Genetics cont. 1. Random breeding 2. No differential migration 3. Large population 4. No mutations 5. No natural selection Given these conditions, the distribution of a pair of alleles can be described by the following equation. p 2 + 2pq + q 2 = 1 This is the Hardy-Weinberg Principle and describes conditions in which there is NO EVOLUTION
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Pop. Exp. RABBIT ISLAND 1000 RABBITS 600 BROWN (B) 400 WHITE (b) 2 phenotypes (brown and white) 3 genotypes BB = brown Bb = brown bb = white Original Colonists were 60% brown; 40 % white
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Allele distribution 1 BB = brown 100 Bb = brown 400 bb = white 2 alleles/ rabbit: Therefore 2000 genes = gene pool # genotypes # genes gene frequency 1 BB 100 Bb 1000 100 100 800 1100 900 55% B 45% b
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Gene Frequencies p = Fraction of gene pool with dominant trait p = 0.55 q’ = Fraction of gene pool with recessive trait q = 0.45 Total gene pool: p + q = 1.00 0.55 + 0.45 = 1.00
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This note was uploaded on 12/09/2009 for the course BIO 200 taught by Professor Herreid during the Spring '07 term at SUNY Buffalo.

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Population Genetics - Review Evolution occurs by: Acquired...

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