Lecture 5 --> Hardy-Weinberg Principle

Hardy-Weinberg Principle

a null model that makes predictions about genotype frequencies given some set of allele frequencies

Hardy-Weinberg Assumptions

1. random mating
2. no natural selection
3. no migration (gene flow)
4. no mutation
5. population is v large (no genetic drift)
--> assumes that allele frequencies NEVER change (no evolution)
--> holds remarkably well in pops.

Hardy-Weinberg assumes...

tha the ONLY thing changing genotype frequencies are Mendel's Laws (segregation/random union)

PollEv Question - The Hardy-Weinberg Principle assumes which of the following?

A) Directional Selection
B) Non-random mating & Segregation of Alleles
C) Random Mutation
D) Genetic Drift is strong
E) None of the above

E) None of the above

Hardy-Weinberg Equation

p^2 + 2pq + q^2 = 1
--> shows expected frequencies, which can then be used to find expected counts

Chi-Squared Test

compares observed and expected values, allowing for some amount of error
--> shows how likely we are to get our X^2 by CHANCE!
--> significant deviation (high x^2) means one of the assumptions is violated

Chi-Squared Test - Repeat

we repeat this test to build a distribution of expected values from many random samples

Evolutionary Implications of HW

SLIDES 50/51

Hardy-Weinberg Equilibrium

when expected frequencies are reached, they will NOT change
--> beforehand, it takes only one generation of HW assumptions to restore the expected frequencies