Population Genetics Lab Report PDF

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Dr. Goupil...

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BIO LAB 105 Population Genetics Lab

Experiment _______________________ Stimulation of ___________________________ Generation

Allelic Frequency

Genotypic Frequency

p

q

p^2

2pq

q^2

0

0.50

0.50

0.25

0.50

0.25

1

0.58

0.42

0.336

0.4872

0.1764

2

0.62

0.38

0.3844

0.4727

0.1444

3

0.63

0.37

0.397

0.466

0.137

4

0.65

0.35

0.423

0.455

0.122

5

0.66

0.34

0.435

0.449

0.115

Discussion Questions 1-6: 1. Which of the conditions that are necessary for the Hardy-Weinberg equilibrium were met? In order to maintain equilibrium, conditions had to be met. These conditions included random mating, no natural selection, no gene flow, and no mutations.

2. Which condition was changed? The only condition that was not met was not having genetic drift. Considering that the population remained small generations after generations, genetic drift did not occur.

3. Briefly describe the scenario that your team stimulated. In order to carry out each generation and their allele frequency, a combination of 50 red beads and 50 yellow beads were put into a bag. The red beads represented dominant (A) while the yellow beads represent recessive (a). Two beads were selected at random, either representing AA, Aa, or aa. This process was done 6 times to represent 5 generations. Overtime, the allele frequency for p and q changed, but remaining close to 0.50 for both p and q.

4. What were your predicted results? According to the Hardy-Weinberg theorem, equilibrium occurs when the frequencies (results) remain the same throughout generations. The predicted results included an allele frequency of 0.50 for both p (A) and q (a). However, since Hardy-Weinberg did not occur, meaning equilibrium did not occur, the frequencies for both p and q as well as the genotypic frequencies, increased overtime (AA) and decreased overtime (Aa, aa).

5. How many generations did you stimulate? A total of 6 generations were stimulated.

6. Sketch a graph of the change in p and q overtime. You should have two lines, one for each frequency.

7. Describe the changes in allele frequencies p and q overtime. Did your results match your predictions? As soon on the graph, through the course of 6 generations, the allele frequency of both p and q change. For the initial generation, the allele frequency for both p and q was at 0.50, meaning half the population was composed of dominant (A) and the other half recessive (a). However, as generations passed, we can see a trend in allele frequency for p in which it increases, while q

decreases. Based on the results, we can conclude that the results from the table are accurate as those who are heterozygous are sickle cell die out, therefore, explaining the decrease in heterozygous frequency. Those who inherited the homozygous dominant trait for sickle cell still died out, but at a lower rate in comparison to those who were heterozygous and homozygous recessive.

8. Describe the changes in the genotypic frequencies. Considering that the allele frequencies for p and q changed overtime, so did the genotypic frequencies. The initial population started off with 25% being homozygous dominant, 50% heterozygous, and 25% homozygous recessive. Overtime, the frequency for homozygous dominant increased while the frequency for homozygous recessive decreased. As for the heterozygous genotypic frequency, it decreased, but very slowly, and not as drastic as the genotypic frequency for that of homozygous recessive. For generation 4, the frequencies for homozygous dominant and heterozygous come extremely close.

9. Compare your final allelic and genotypic frequencies with those of the starting population. The starting population consisted of 50% dominant (A), 50% recessive (a) with the genotypic frequencies of 25% for homozygous dominant, 50% for heterozygous, and 25% homozygous recessive. As for the ending population, generation 5, the allele frequency changed to 66% for dominant (A) and 34% for recessive (a). As for the genotypic frequencies, homozygous dominant changed to 43.5% for homozygous dominant, 44.9% for heterozygous, and 11.5% for homozygous recessive. Based on these results, it proves the initial prediction to be true that homozygous dominant p^2 (AA) will increase overtime while both heterozygous (2pq) and homozygous recessive q^2 (aa) will decrease due to the fact that the sickle cell disease highly impacts the change in frequencies for those who are heterozygous and homozygous recessive for the trait.

PCR Protocol, Questions 6d & 8:

6d. Use the table of allele frequencies to calculate the expected frequency of each genotype found in Question 5. Determine the frequencies for each population show in the table.

Individual

Genotype

U.S Caucasian

African American

U.S Hispanic

1

17, 23, 84

0.008

0.0002

0.00000039

2

23, 27, 84

00.00000052

0.00000299

0.00000012

3

23, 30, 24

0.00000064

0.00000368

0.000000165

4

23, 80

0.0008

0.00046

0.00003

8. For identification purposes, crime laboratories have settled on a panel of thirteen highly variable short tandem repeat (STR) loci, which are amplified together in a capillary electrophoresis chip. Since the loci are located on different chromosomes, they are thought to be unlinked - that is, they are inherited independently of each other. Thus, the probability of inheriting a given set of alleles at the thirteen loci is the product of their individual probabilities. A sample of only six loci is listed below. Assuming Hardy-Weinberg equilibrium, calculate the probability of the following genotype occurring. What does this show you about the power of using multiple loci?...