Chapter 17 Population Genetics

# Chapter 17 Population Genetics - Population Genetics...

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Population Genetics Suggested problems: #1, 2, 3, 4, 7, 10, 11 (a, b), 15

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Genetic Variation on the population level: Can be estimated in various ways: protein electrophoretic mobility shift RFLPs VNTRs karyotyping (chromosome-level variation) For most species: 1.In the population, about 1/3 of all genes are polymorphic (different alleles present in the population) 1.In a given individual, ~1/10 of all genes are heterozygous.
Calculating Allele Frequencies in a population each individual carries two copies of each autosomal allele, therefore is counted twice in calculating allele frequencies total number of alleles is 6129x2=12,258 6129 total p = frequency of L M = [2(1787) + 3039]/12258 = 0.54 q = frequency of L N = [2(1303) + 3039]/12258 = 0.46 p + q = 1 when there are two different alleles when there are more than two alleles, the sum of all the frequencies equals one for X-linked alleles, males only have one allele, females have two

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Remember: allele frequencies are different than genotype frequencies! Calculating allele frequencies from genotype frequencies: p= allele frequency of A = genotype frequency (A/A) + ( ½) genotype frequency A/a ) 0.835 + (1/2)(0.156) = 0.913 Allele frequencies vary in different human populations
The Hardy-Weinberg principle Independently predicted by Hardy and Weinberg in 1908 Genotype Frequency AA p 2 Aa 2pq aa q 2 Where p= allele frequency of A q=allele frequency of a Meiotic segregation in randomly mating populations leads to an equilibrium distribution of genotypes after only one generation. *allele frequencies will remain constant in the population

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Problem: The incidence of PKU in the United States is 1 in 10,000. What is the allele frequency, and what percent of individuals are carriers? q 2 = 0.0001 q = 0.01 p = 1- 0.01 = 0.99 carrier frequency = 2pq = 2(0.99)(0.01) = 0.0198 = ~2% Problem: The allele frequency for X-linked color blindness is q = 0.12. What is the chance that a man will be color blind? What is the chance a woman will be a heterozygote carrier? What is the chance that a woman will be color blind?
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## This note was uploaded on 05/28/2011 for the course BIO 220 taught by Professor Dr.leatherman during the Spring '10 term at N. Colorado.

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Chapter 17 Population Genetics - Population Genetics...

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