MBLG2972 Lecture Notes - Lecture 9: Genetic Drift, Zygosity, Chi-Squared Distribution
5 Jul 2018
School
Department
Course
Professor
MBLG2072
Genetics and Genomics
Monica Zanuttini !
460381099
Lecture 9 Hardy-Weinberg Law
Hardy Weinberg law: In a large population and in the absence of mutation, selection or migration,
allele and genotype frequency will remain constant from one generation to the next.” !
What causes perturbation? !
•Migration (only if the genotype of migrants are different to those that already exist). !
•Mutation (too slow to be important, at the scale we are talking about). !
•Selection !
•Inbreeding!
Detection of perturbations: !
1. Work out allele frequencies.!
2. Work out expected frequencies. !
3. Work out the fit of the expected numbers (not frequencies) to the observed. !
$$ Larger chi square value = smaller P value. !
Document Summary
Hardy weinberg law: in a large population and in the absence of mutation, selection or migration, allele and genotype frequency will remain constant from one generation to the next. What causes perturbation: migration (only if the genotype of migrants are di erent to those that already exist), mutation (too slow to be important, at the scale we are talking about), selection, inbreeding. Detection of perturbations: work out allele frequencies, work out expected frequencies, work out the t of the expected numbers (not frequencies) to the observed. Larger chi square value = smaller p value. Walhund e ect: 2 populations di erent allele frequencies mix, causes a deviation of expected genotype frequencies from that predicted, detected as a de cit of heterozygotes, this is how you can tell if we have had recent migration. Genetic drift: loss of heterozygosity, eventual xation.
