How can allele frequencies be derived from genotypes ?
What are the 5 core assumptins of the Hardy-Weinberg model ?
no mutation
random mating
no gene flow
infinite population size
no selection
u = 0
m = 0
r = 0
N = ∞
s = 0
Does the allele frequency vary accross generations in the Hardy-Weinberg equilibrium ?
No
This means that even the frequency of recessive genes does not decrease
Give the main equations of the HWE
D = f AA = P(AA) = p^2
H = f Aa = P(Aa) = 2pq
R = f aa = P(aa) = q^2
p = Allele A frequency = D + H/2
q = Allele a frequency = R + H/2
How are genotype frequencies related to allele frequencies
Related via the HWE
Allele freq can be infered from Genotype freq
Genotype freq can be infered from Allele freq
How can the HWE used for hypothesis testing ?
HWE is used as the null model (expected values)
Null hypothesis is that the observed data does not deviate from observed n
Testing e.g. by X-square
What are some major reasons for deviations from the HWE ?
Assortative mating (mating with same genotypes)
Inbreeding
Population structure
Selection
Muatation and Genetic Drift
What is assortative mating ?
individuals with same or similar genotype may be more likely to mate with each other
Opposite: dis-assortative / negative mating
What happens through assortative mating with the HWE ?
Reducttion of Herterozygotes halfed after each generation
Number of Homozygotes increases
Allele frequency does not change
Homozygote frequency approaches respective allele frequency
Which effect does inbreeding have on the HWE ?
similar to assortative mating
but affects all loci, not just those responsible for assortative mating
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