Population Genetics.

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Population Genetics

Population group of individuals of the same species, found in the same time and place and are able to interbreed.

Gene Pool the total of all alleles of all genes in the population OR for a single gene the total of all the alleles of that gene that occur in a population.

Allele Frequency frequency of a certain allele in a population of breeding organisms. Example: if a population is 100% heterozygous for seed shape with the genotype Rr The frequency of R is 50% or .5 The frequency of r is 50% or .5

Population genetics A population of 100 individuals has 50% Rr 25% RR What are the allele frequencies?

Population genetics A population of 100 individuals has 50% Rr 25% RR What are the allele frequencies? How many R are there in the population?

Population genetics A population of 100 individuals has 50% Rr 25% RR What are the allele frequencies? How many R are there in the population? 50 (from the Rr) and 50 from the RR (2*25) 100 R out of how many total alleles?

Population genetics A population of 100 individuals has 50% Rr 25% RR What are the allele frequencies? How many R are there in the population? 50 (from the Rr) and 50 from the RR (2*25) 100 R out of how many total alleles? 100/200 alleles = 50% or .5

Population genetics A population of 100 individuals has 50% Rr 25% RR What are the allele frequencies? How many r are there in the population? The same 50 + 50 =100 / 200 = .5

Allele frequencies should add up Allele frequency of R is .5 Allele frequency of r is .5 If these are the only two alleles for one trait in the population, then they should add up to 1 .5 R + .5 R = 1

Genetic equilibrium a hypothetical state in which a population is not changing genetically because the allele frequencies remain constant over time.

A2 + 2AB + B2 = 1 This equation helps determine if a population is in genetic equilibrium by determining the outcome of random mating in the population Where A represents the frequency of the one allele and B represents the frequency of the other. The first term A2 is the percent of the population that will be homozygous dominant The second term 2AB will be the percent that will be heterozygous The third term B2 is the percent that will be homozygous recessive.

A2 + 2AB + B2 = 1 Is our Hypothetical population in Equilibrium? A population of 100 individuals has 50 Rr Frequency of R = .5 25 RR Frequency of r = .5 25 rr Does .52 + 2 (.5) + .52 = 1?

A2 + 2AB + B2 = 1 Is our Hypothetical population in Equilibrium? A population of 100 individuals has 50 Rr Frequency of R = .5 25 RR Frequency of r = .5 25 rr Does .52 + 2 (.5*.5) + .52 = 1? .5+2(.25)+ .5 =1 yes!

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