http://faculty.washington.edu/herronjc/SoftwareFolder/software.html and download
ID: 142957 • Letter: H
Question
http://faculty.washington.edu/herronjc/SoftwareFolder/software.html and download these two software packages: AlleleA1. Use them to conduct these this exercises.
I have done this four times and I'm still getting the wrong answer.
Allele A1. When you open the software you will see a single set of axes, with Generation on the x axis and Frequency of allele A1 on the y axis. This is a simple simulation showing the behavior of two alleles at a single locus over time. For this first simulation, we will leave all of the parameters in the neutral position in which they start, with both alleles equally common (starting frequency of each = 0.5), fitnesses all equal to 1, no mutation, no migration, random mating). We will vary only population size, which begins as infinite.
For the Graph Lines choice in the lower right, choose Auto. This allows you to overlay multiple lines on a graph, each in a different color.
With all choices in default settings (except Graph Lines = Auto), push the “Run” button on the bottom left. You will see the line move across the graph unchanging, with Allele A1 frequency remaining at 0.50 over 500 generations. This illustrates the Hardy Weinberg equilibrium, the combination of factors when allele frequencies will not change.
Now do the following:
1. Change the population size from infinite to 1000. Leaving the Graph Lines set at Auto, run 8 lineages through 500 generations each. They will show up as 8 lines of different colors. For each of the 8 lineages, record the allele A1 frequency at 500 generations by checking the history (click on the small triangle in the upper right). For any lineage that reached fixation (allele frequency of either 0 or 1), record the generation number at which fixation was reached. You will be asked to summarize these data in the table below.
a. Change the population size from 1000 to 500 and repeat the 8 lineages of 500 generations each (when you reset, remember to switch back to “auto” in the lower right when you change your population size).
b. Change the population size from 500 to 100 and repeat the 8 lineages of 500 generations each.
c. Change the population size from 100 to 50 and repeat the 8 lineages of 500 generations.
Complete the data table, from the perspective of allele A1:
Population Size
(8 lineages will be run for each population size)
A. Number of lineages reaching fixation at 1 (all alleles = A1)
B. Number of lineages reaching fixation at 0 (all alleles = A2)
C. Mean generation at which fixation reached
D. Mean final allele frequency
E. Range of final allele frequencies
Infinite
1000
500
100
50
Population Size
(8 lineages will be run for each population size)
A. Number of lineages reaching fixation at 1 (all alleles = A1)
B. Number of lineages reaching fixation at 0 (all alleles = A2)
C. Mean generation at which fixation reached
D. Mean final allele frequency
E. Range of final allele frequencies
Infinite
1000
500
100
50
Explanation / Answer
The effect of genetic drift is different
depending on the size of the population Drift is more
intense (alleles are fixed or lost more
quickly) in smaller populations (see yellow
populations, population size 10, in the figure @ right). Therefore, in a population of size 100 (green lines),
the genetic drift is stronger than in a population of size 1000 (blue lines) and the A1 allele is fixed or lost
more easily Keep in mind that in a population size of 1,000 and 10,000 (blue and pink lines), the A1 allele is
neither fixed nor lost in these simulations.
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