ALLELE A1 EXERCISES – Genetic Drift
Today's lab will use a computer program to simulate evolution at the population genetic level.
Evolution is often defined as a change in allele frequencies over time. The program tha
...
ALLELE A1 EXERCISES – Genetic Drift
Today's lab will use a computer program to simulate evolution at the population genetic level.
Evolution is often defined as a change in allele frequencies over time. The program that we are
using today, Allele A1, shows how the frequency of one allele in a two-allele system changes
over many generations.
How to start Allele A1
Allele A1 is available as freeware from:
http://faculty.washington.edu/~herronjc/SoftwareFolder/software.html
You can download the appropriate version for a Mac or PC. Double click on the icon (or single
click on the icon in the dock), and the program will start up. Click on the ad for the textbook to
get rid of it.
Reading the output
Allele A1 provides a plot of each run that graphs the frequency of one allele (A1) over the
specified number of generations. Note that the frequency goes from zero to 1.0. Although the
frequency of the second allele (A2) is not given, it can be inferred by subtracting the frequency
of A from 1.0. You can view frequencies of the other allele (A2) or of the genotypes by clicking
on the arrow at the left of the display and selecting the appropriate option. Note that the alleles
are given as A1 and A2, because we are not (yet) assuming that one allele is dominant to the
other.
Setting parameters
Allele A1 allows you to manipulate a number of parameters and other aspects of the program.
Parameters include the initial frequency of A1, mutation rate of A1 (to A2) and A2 (to A1),
fitness of different genotypes, and migration rate. You can also set the number of plots that
will be shown on the screen simultaneously. Set this value to multiple. Each time you run
the program, be sure to choose a new color from the row of colored boxes, so that you'll be
able to view results of different runs more easily.
Hardy-Weinberg Equilibrium and its Violations
The Hardy-Weinberg Equilibrium (HWE) is the prediction that populations will not change in terms of
allele and genotype frequencies in the absence of evolutionary causes. Thus, Hardy-Weinberg equilibrium
occurs if:
There is no mutation of alleles (the mutation rate of both alleles = 0),
There is no migration into the population from elsewhere (the frequency of migrants each
generation = 0),
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