Biology students will use the Hardy Weinberg Classroom Model Net Logo program created by Kenneth Letendre. They will use the computer simulation to analyze how variables such as the proportion of alleles, population size, and selection against alleles can influence the genetics of a population. The Hardy Weinberg principle predicts the genotype and phenotype frequencies given that five assumptions (large population size, mating is random, no mutations, no migration, and no selection) hold true in a population.

You will need the following resources to complete this assignment.

• NetLogo Hardy Weinberg Model

Hardy Weinberg Population Genetics

In 1908 G.H. Hardy and W. Weinberg independently suggested a scheme whereby evolution could be viewed as changes in the frequency of alleles in a population of organisms. In this scheme, if (A) and (A) are alleles for a particular gene locus and each diploid individual has two such loci then (p) can be designated as the frequency of the (A) allele and (q) as the frequency of the a allele. Thus in a population of 100 individuals (each with two loci) in which 40% of the alleles are (A), (p) would be .40. The rest of the alleles (60%) would be (a), and (q) would be .60. (i.e. p + q = 1.0).

These are referred to as allele frequencies. The frequency of the possible diploid combinations of these alleles (AA, Aa, and aa) is expressed as (p² + 2pq + q² = 1.0).

Hardy and Weinberg also argued that if five conditions are met, the populations allele and genotype frequencies will remain constant from generation to generation. These conditions are as follows:

1. The breeding population is large.
2. Mating is random.
3. There is no mutation of the alleles.
4. No differential migration occurs.
5. There is no selection.

Purpose

Students will learn about the Hardy Weinberg law of genetic equilibrium. The students will study the relationship between evolution and changes in allele frequency of a population by using the Net Logo Hardy Weinberg computer modeling simulation.

Learning Objectives

1. Understand how natural selection can alter allelic frequencies in a population.

2. Apply the Hardy Weinberg equation and its use in determining the frequency of alleles in a population.

3. Analyze the effects on allelic frequencies of selection against the homozygous recessive population or other genotypes.

4. Explain natural selection and other causes of microevolution as deviations from the conditions required to maintain Hardy Weinberg equilibrium.

Procedure Need to take initial readings as well to compare and totals are important.

Using the Net Logo Hardy Weinberg model you will run a simulation of a population of randomly heterozygous individuals with an initial gene frequency of 0.5 for the dominant allele (A) and the recessive allele (a).

1. Before moving on spend 5 minutes familiarizing yourself with how the model works by... 
2. Set up your population size to 500.
3. On the bottom left side of your simulation set your max- generation to 100.
4. Select the species you would like to observe... turtles, humans, etc...
5. Click on the “set up” button.
6. Collect initial data in the data table before moving on.
7. Click on “go.”
8. Monitor the population closely by observing the species and graphs (genotype, phenotype, and allele)
9. Analyze the data after 100 generations and complete the table below.

Thank goodness for computer simulations!

In this case II you will modify the simulation to make it more realistic. In the natural environment, not all genotypes have the same rate of survival; that is, the environment might favor some genotypes while selecting against others. An example, is the human condition of sickle cell anemia. This is a disease caused by a mutation on one allele, and individuals who are homozygous recessive often do not survive to reach reproductive maturity. For this simulation you will assume that the homozygous recessive individuals never survive (100% selection against) and that heterozygous and homozygous dominant individuals survive 100% of the time.

Procedure

1. Using the Net Logo Hardy Weinberg model you will run a simulation of a population of randomly heterozygous individuals with an initial gene frequency of .5 for the dominant allele A and the recessive allele a.

2. Set up your “population size” to 500.
3. On the bottom left side of your simulation set your “max- generation” to 100.
4. Select the species you would like to observe... turtles, humans, etc...
5. Move the “selection against yellow” slider to 100%

6. Click on the “set up” button.             
7. Click on “go.”
8. Monitor the population closely by observing the species and graphs (genotype, phenotype, and allele)
9. Analyze the data after 100 generations and complete the table below.

Case II Selection Data Analysis

Use the Hardy Weinberg equations to answer the following questions

p + q = 1

p² + 2pq + q² = 1

p = frequency of dominant allele

q = frequency of recessive allele

p² = frequency of homozygous dominant genotype

q² = frequency of homozygous recessive genotype

2pq = frequency of heterozygous genotype