Double-click the genx icon start the program

4. Using Windows Explorer, Click on the Labshare folder, then on Biology 303 folder, then on the GenX icon to start.

A. Recall from lecture:

Generation X is a computer model of evolution. It allows you to alter the four
evolutionary forces, either one at a time or in combination, and see the effect on genotype and allele frequencies.

C. Basic Operation of GenX to simulate population genetics.

If you’ve changed any numbers, you can quickly restore the defaults: click RENINITIALIZE ALL TO DEFAULT under the OPERATE menu.

2. Under OPERATE, click RUN. The arrow key near the top left does the same thing.

D. Population size and the rate of genetic drift:

A common rule of thumb in conservation biology (Franklin 1980) is that a population size of at least 500 is needed to preserve genetic variability, so that the population can respond to future changes in environmental conditions. Recently, Lande (1996) argued that a population size of 5000 is a more realistic target.

2. In the OPERATE menu, click the REINITIALIZE ALL TO DEFAULT 3. Set population size to 500 for population 1 and to 50 for population 2.

4. Make sure all the other buttons read “Inactive”
5. In the OPERATE menu, click RUN
6. RUN as often as needed to answer the above questions.

To investigate how dispersal affects drift within a population and evolutionary divergence between populations, first set up a simulation with all evolutionary forces inactive:

1. Under OPERATE click REINITIALIZE ALL TO DEFAULT. 2. Set Population 1 to 200 individuals.

4. Set DISPERSAL ACTIVE for both populations.

5. Set DISPERSAL RATE = 0.01 for both populations. (This means that individuals have a 1 in 100 likelihood of dispersing.)
6. RUN

9. Set DISPERSAL ACTIVE for population 1 and DISPERSAL INACTIVE for population 2.

10. RUN

13. RUN, and note the results to compare with the next run.

14. Now set DISPERSAL RATE = 0.10 for population 1 (increasing the rate of dispersal from population 1 to population 2 by a factor of 10, with everything else held constant).

Selection against a recessive harmful allele:

Selection against a dominant harmful allele:

1. Under OPERATE, click REINITIALIZE ALL TO DEFAULT. 2. Set NATURAL SELECTION to ACTIVE in population 1.

How do allele frequencies differ between the populations?

Selection against an additive harmful allele:

How do allele frequencies differ between the populations?

p is the frequency of the A allele
q is the frequency of the a allele.

IF the population is in HW equilibrium, the genotype frequencies in the next generation will be:

Questions to consider:

1. How does the length of time over which drift occurs affect the likelihood of an allele drifting to fixation (frequency of 0 or 1)? How does population size affect the likelihood of an allele drifting to fixation? How does dispersal among populations affect the likelihood of an allele drifting to fixation?