monday, september 10, 2012

Monday, September 10, 2012

Purpose of H-W Principle:

The Hardy-Weinberg Principle provides a baseline for comparison &

determines whether or not gene frequencies have changed in a population and thus whether

(micro)evolution has occurred.

Hardy-Weinberg Assumptions

• Very large population size

• No migration

• No net mutation

• Random Mating

• No natural selection

Hardy-Weinberg Equations:

p = frequency of allele 1 in gene poolq = frequency of allele 2 allele in gene pool

Frequencies can be expressed as decimals (0.4) or percentages (40%)

p + q = 1

Hardy-Weinberg Equations:Allele frequency is used to predict genotype frequency (%) for a randomly mating population

Homozygous for allele 1 = p • p = p2

Homozygous for allele 2 = q • q = q2

Heterozygous = p • q or q • p = 2pq

p2 + 2pq + q2 = 1

Hardy-Weinberg Lab

• Instructions dictate initial allele frequencies of:–p = 0.5–q = 0.5

• If there are 28 Teddy Grahams in your population, how many should be pp? pq? qq?

• Explain how you determined your answer.

Teddy Grahams mate randomly. All bears areequally attractive.

Though they live a good life, it is short. After having 2 babies, they die keeping the population size constant.

All bears are equally in danger of predation due to their yumminess

Teddy Graham Genetics

• Today you will be helping Teddy Grahams to procreate.

• Reminder of the genetic rules:– When honey and honey mate, 2

Honey are born– When honey and chocolate mate,

2 speckled are born– When honey and speckled mate,

One honey and one speckled are born – When chocolate and speckled mate,

One chocolate and one speckled are born

When Speckled and Speckled mate

• Use the allele cards. Each speckled has a p and a q allele• Pick one allele for each parent to give• This determines the genes of the first offspring• Return the cards to the parent and pick again for the

second offspring

• Allow 5 generations to mate. • Fill in the data chart and calculate allele

frequencies at the end of 5 generations• Conduct a Chi Square test to see whether the

number of bears of each type you expect to have if allele frequencies did not change, differs from the observed (actual) number of each type you have