Biology 130 – Molecular Biology and Genetics
Polymerase Chain Reaction Assignment: Allele Frequencies
This worksheet, and the components to attach are to be completed individually. It is due March 6th, 4:00pm
Name:
Lab Section:
For this assignment you will need to generate a standard curve for each ladder used. Attach gel photos,
standard curves, and a table of results for all bands in your section lab section.
1. Determine and report the sizes of your D1S80 products (base pairs and number of repeats) and your
TPA-25 genotype. Are you homozygous for both, TPA-25 only, D1S80 only, or heterozygous for both?
2. Determine the TPA-25 genotype distribution for your lab section—how many students are homozygous
for the TPA-25 300bp intron, how many are homozygous for the lack of 300bp intron, and how many
are heterozygous?
3.
Determine the allele frequencies of the lab section. Label the with-intron as p and the without intron as
q.
4. Populations that are genetically stable will have constant allele frequencies from generation to
generation: the population will be in Hardy-Weinberg Equilibrium. Using the Hardy-Weinberg
equation and the allele frequencies above, calculate the expected genotype frequencies.
5.
We can examine the differences between expected and observed genotype frequencies using the Chisquared test(2). This should be familiar from the FlyLab. Now you will do the test by hand—it is very
straight forward.
observed frequency  expected frequency 2
2  
expected frequency
 indicates “sum of”
You have three observed genotype frequencies and three expected genotype frequencies. Calculate each
and
observed frequency  expected frequency 2 add them together to arrive at the Chi-Square.
expected frequency
6. Compare the value you calculated to the value from the Chi-squared table, dependent on how many
groups are compared. With three groups the critical value is 2 =5.99. If the calculated value is less than
5.99 accept the null hypothesis (that there is no difference between the expected and observed values:
the population is in Hardy-Weinberg Equilibrium. If the value calculated is greater than or equal to 5.99
reject the null hypothesis (the population is not in Hardy-Weinberg Equilibrium).
Based on your calculated 2 , is your lab section in Hardy-Weinberg Equilibrium?
7. What are three factors that disrupt Hardy-Weinberg Equilibrium that could affect the lab section
(regardless of the results above)?