Lecture 22 - Population Genetics The study of Genetic...

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Population Genetics The study of Genetic variations within populations, and the factors that influence these variations. Factors include: 1) Mating Patterns 2) Migration 3) Mutation 4) Recombination 5) Natural Selection (fitness) 6) Random Events
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Types of Variation Phenotypic Variation – Differences in a trait found in populations. For example, eye color, stripes on a zebra, or spots on a leopard. Nucleotide Polymorphisms – Differences in nucleic acid sequences found in a population. Can be assayed by PCR, Southern Blotting, Sequencing. Amino Acid Polymorphisms – Differences in amino acid sequence found within a population. Can be detected elctrophoretically, or antigenically.
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Willie Shoemaker: 100 lbs, 4’ 11”, pale exterior Born August 19, 1931 Fabens TX Wilt Chamberlain: 275 lbs, 7’1”, less pale Born August 21, 1936 Philadelphia PA Phenotypic variation in Americans
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Selective Breeding can increase such differences
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Apatura iris Purple Emperor Butterfly Sexual Dimorphism Phenotypic Variation
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Nucleotide Polymorphisms Restriction-site Variation: 4 base cutters = site every 4 4 = 256 base pairs 6 base cutter = site every 4 6 = 4096 Survey of 4 base cutter polymorphisms in the rosy gene of Drosophila pseudoobscura Can Also use 1) single nucleotide polymorphisms-SNPs 2) Minisatellites, 3) Microsatellites, etc….
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Amino Acid Polymorphisms
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Genotype and Allele Frequencies Genotype frequency: ƒ A/A = frequency of AA genotype ƒ A/a = frequency of Aa genotype ƒ a/a = frequency of aa genotype p = frequency of the A allele p = ƒ A/A + ½ (ƒ A/a ) q = frequency of the a allele q = ƒ a/a + ½ (ƒ A/a ) p + q = ƒA/A + ½ (ƒA/a) + ƒ a/a + ½ (ƒ A/a ) p + q = ƒA/A + ƒA/a + ƒa/a = 1 q = 1 - p
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Allele Frequency Forest/Grassland Margin Genotypes PK/PK PK/ pk pk/pk Freq. # in Pop 10 20 10 # of Pk alleles 20 20 0 40/80 =0.5 # of pk alleles 0 20 20 40/80 =0.5 p = frequency of the PK allele p = ƒPK/PK + ½ (ƒPK/pk) p = 10/40 + ½(20/40) = ¼ + ¼ = ½ q = frequency of the A allele q = ƒpk/pk + ½ (ƒPK/pk) q = 10/40 + ½(20/40) = ¼ + ¼ = ½
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Allele Frequency Deep Forest Genotypes PK/PK PK/
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Lecture 22 - Population Genetics The study of Genetic...

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