BSC 219
Population Genetics
11/29/12
25.1 Genotypic and Allelic Frequencies Are Used to Describe
the Gene Pool Of a Population
Calculating
genotypic frequencies
F = No.AA individuals/N
N: total
no. of individuals
F:
frequency of AA alleles.
Calculating
allelic frequencies
Frquency of an
allele = No. copies of the alleles/No. copies of all alleles at the locus in a population.
Hardy-Weinberg
Law
Assumption: population is large, randomly mating, not affected by
mutation, migration, or natural selection.
Prediction
1: the allelic frequencies of a population do not
change.
Prediction
2: the genotypic frquencies
stabilize.
p + q = 1
p2 + 2pg +
q2 = 1
P2:
homozygous dominant allele pair frequency.
Q2 :homozygous recessive allele pair frequency.
2pq:
heterozygous allele frequency.
Easiest to solve by focusing on recessive
phenotype since that means homozygous recessive genotype.
25.3 Nonrandom Mating Affects the Genotypic Frequencies of a
Population
Positive
assortative mating:
a tendency of like
individuals to mate.
Negative
assortative mating:
A tendency of unlike individuals to mate.
Inbreeding
Increases
frequency of homozygotes in population
Rate is
affected by how closely related mating pairs are
Concept Check 2
25.4 Several Evolutionary Forces Potentially Cause Changes in
Allelic Frequencies
Mutation
Migration
Genetic
Drift
Founder
effect
Genetic
bottle neck
Natural
selection-not all
genotypes and corresponding phenotypes are as successful in nature.
Can
calculate changes in allele frequency with each new generation under selective
conditions