Is this population a single sexually reproducing population? ECL 290 Use of population genetic software Spring 2004 Melinda Baerwald Marilia Burle Judah Grossman Rachel Schwartz

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Is this population a single sexually reproducing
population?ECL 290Use of population genetic
softwareSpring 2004Melinda BaerwaldMarilia
BurleJudah GrossmanRachel Schwartz
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Polymorphism different alleles for a locus
across individuals. Monomorphism not
polymorphic
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Allele and genotype frequencies
Allele frequencies 187 9/16 0.56 183 3/16
0.19 185 4/16 0.25
Genotype frequencies (observed genotype
frequencies) 187/187 3/8 0.375 183/183 1/8
0.125 185/185 1/8 0.125 187/183 1/8
0.125 187/185 2/8 0.25 185/183 0
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Hardy-Weinberg Describes equilibrium sate of a
locus in a randomly mating diploid population,
free of other evolutionary forces.
Assumptions . Randomly mating population . No
mutation, no migration, no genetic drift, no
selection.
Expected genotype frequencies (equilibrium
reached fast, in a single generation of random
mating) p 187 allele freq. q 183
allele freq. r 185 allele freq. 187/187
183/183 185/185 187/183 187/185 185/183
p2 q2
r2 2pq 2pr 2rq

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Observed and expected heterozygosities Testin
g Hardy-Weinberg Test differences between
observed and expected frequencies, example
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If not in H-W equilibrium? 1. Most of the loci
NOT H-W Excess homozygosities -Inbreeding -Wah
lund effect pooled subpopulations that do not
interbreed as a single mating unit -Null alleles
? In many locus? -Loci are under
selection Excess heterozygosities -Isolate
breaking subpopulations make contact and
interbreed average homozygosity temporarily
decreases -Overdominant selection
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2. 1 or few loci NOT in H-W -Null alleles
(excess of homozygosities) -locus specific
selection Larger of loci increase power on
testing H-W- if loci not linked. Violation of
H-W frequently due genotyping errors allelic
misassignments, allelic dropout control in H-W.
When H-W is found NOT all assumptions valid
(some migration, mutation, selection) conclude
single random mating population.
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Application of H-W knowing the frequency of
recessive alleles estimate the other genotype
frequencies dominant data