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### Evolution

Hardy-Weinberg Principle

Intro

- Last day we left off talking about populations…
- Populations geneticists are able to quantify the total number of alleles within a population ==this is known as the gene pool
- They are able to accomplish this by measuring each allele frequency, which is the proportion of gene copies in a population for a given allele
- Therefore evolutionary changes in populations can be quantitatively measured by looking for changes in allele frequencies

Example

Hmmm…

- In terms of evolution, would the dominant form of a moth wing become more and more common over time?
- Do allele frequencies remain constant or change over time?
- These questions were answered independently (think Darwin vs. Wallace) by a mathematician named Hardy and physicist named Weinberg== thus Hardy-Weinberg principle

The Principle

- Allele frequencies will not change over time (generation-generation) if the following conditions are met:
- The population is very large
- Mating opportunities are equal
- No mutations occur
- No migration occurs
- All individuals have an equal chance at reproductive success==no natural selection

Equation

- The H-W-P is often expressed using the following equation (for a gene with only 2 alleles==A/a):
- let p=frequency of A and q=frequency of a, then
p+q=1

(p+q)2= 1

p2 + 2pq + q2 = 1, where

p2= frequency of AA; 2pq= frequency of Aa; and q2 = frequency of aa

Moth example

Note: genotype frequencies will remain the same from generation to generation as long mating is random

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