Evolution Lecture No. 4: Population Genetics II
Monday September 17 , 2012
Punnett Square For A Population:
-Describes the resultant genotypes for 100 offspring. Cross between the alleles present in 20
hypothetical gametes (10 sperm and 10 eggs). The results may also be represented as probability values
“p” and “q.”
The Fate Of Alleles:
-A record of what major events occur in the life cycle of a gamete: two gametes form a germinated
zygote, zygotes develop into juvenile offspring, and offspring reach sexual maturity and start producing
new generation of gametes.
-If the allele frequencies change over a single generation, then evolution has occurred.
The Hardy-Weinberg Equilibrium Principle:
-The Hardy-Weinberg principle is a simple and unlikely model for a population of the same species. It
1. Allele frequencies will not change across generations.
2. If allele frequencies are given by “p” and “q,” the genotype frequencies will be given by p , 2pq and
3. p + q = 1 p + 2pq + q
-The principles will only be seen in a population of the same species if the following assumptions are
Diploid population – all individuals contain diploids in their genotypes.
Sexual reproduction – all individuals reproduce through sexual reproduction.
No evolution – no evolutionary mechanisms are acting upon the population.
Infinitely large population size – no limiting factors to the given population size.
All individuals survive to reproduce – sexual maturity is reached by all individuals.