The Hardy-Weinberg Principles

Changing Populations

Evolution

• Evolution is caused by the changing of populations.

Changing Populations

• Populations change at the genetic level. To get the population to change the gene pool must change.

Gene Pool• Gene pool- all of the alleles in a population

Ex. 500 Flowers (show incomplete dominance)

320 RR (red)

160 Rr (pink)

20 rr (white)

Allele Frequency • Allele frequency is the proportion of each allele

found in the gene pool.

• p = one allele (dominant)

• q = the other allele (recessive)

Ex. What would the allele frequency be for “R” and “r” in the wild flower population?

Hardy-Weinberg Equation

• This equation shows the frequency of each genotype we would expect to see based on the allele frequencies in the population.

• p2 + 2pq + q2= 1

Ex. What would the genotype proportions be in the flower population?

Hardy-Weinberg Equilibrium• If the genotype frequencies in the actual

population match the proportions in the equation, then the population is in Equilibrium and not evolving.

• Ex. Is the flower population Evolving? *

5 conditions • For a population to stay in equilibrium (not

evolve) five things must be true.

• 1 No Mutations

• 2 Random Mating (no sexual selection)

• 3 No Natural Selection

• 4 No Gene flow

• 5 Very Large Population (no Genetic Drift)

• These five things change the proportion of genotypes or the allele frequencies

Example• In a population of 300 Snakes 130 are

homozygous dominant for black scales. 70 are homozygous recessive and have red scales. 100 are Heterozygous are have a checker board pattern. Is this population evolving?