Hardy-Weinberg Lab Report
Hardy-Weinberg Lab Report
Kevin Suarez, Allison Dame, Jalen Huang
Abstract
The Hardy-Weinberg law of genetic equilibrium was examined by testing the allelic frequencies in bunny populations that were not in equilibrium. In these cases, the populations were not in Hardy-Weinberg equilibrium due to a change in allele frequency. The allele frequency was observed by randomly mating the population, removing the individuals that were selected against and mating the subjects again. This was done for a many trials to determine the allele frequency and examine the Hardy-Weinberg law. The results we observed showed that our experiment supports the Hardy-Weinberg law of genetic equilibrium. A population cannot be in equilibrium unless it complies with all 5 of the laws conditions. Since our experiment is not in Hardy-Weinberg equilibrium, we can see the process of evolution.
Introduction
In this lab, we examined the Hardy-Weinberg law of genetic equilibrium by testing the change in allele frequency in a population. The Hardy-Weinberg law says that a population will see no change in allele frequency as long as “it is stable and in genetic equilibrium.” This means that the population will see no evolution. However, the law can only be applied if the population satisfies 5 conditions: a large breeding population, random mating, no mutations that change allele frequency, no immigration or emigration, and no natural selection. In the experiment, our population consisted of bunnies with the traits of fur or no fur. The dominant allele was represented using F while the recessive allele was represented by f. A heterozygous bunny would have fur, while a recessive bunny would not. The bunnies with no fur would die due to the harsh winters. The bunnies dying changes the number of alleles in the gene pool. This loss can be associated with the requirement of no emigration. The bunnies “emigrated” from the population by dying. During each trial, the bunnies would be mated randomly and the recessive individuals would be removed from the population. The objective of the experiment was to assess the change in allele frequency and examine the resulting end population. Our hypothesis stated that all the recessive alleles would be removed by the 10th trial.
We also conducted a second experiment that we created. Our population once again consisted of bunnies, but this time there were a lot less alleles in the population. We were once again getting rid of the recessive individuals after each trial. We hypothesized that because of the huge reduction in number of alleles, the population would die out by the 5th trial because significant effect on the gene pool after the bunnies died.
Methods
We began our experiment by establishing the organism and the traits we were identifying. The organism was once again bunnies with the alleles for fur (F) and the alleles for no fur (f). We collected 10 red beads to represent the dominant alleles and 10 white beads to represent the recessive alleles. We placed them into a bowl and randomly picked two at a time to simulate breeding. We recorded the information into a chart that depicted how many individuals there were for each heterozygous or homozygous pair. At the end of each trial, we removed the homozygous recessive individuals because they were killed off by the harsh winter. We repeated this for 4 trials until all the recessive alleles were killed off. At the end the experiment is now in Hardy-Weinberg equilibrium, proving the Hardy-Weinberg law.
Results
To gain an understanding of the Hardy-Weinberg law, we did 2 experiments using beads the represented dominant and recessive alleles. We would randomly pick out 2 beads, which would represent the genome of the bunny. The bunnies with a homozygous recessive genotype died and could not reproduce. IN the first experiment we saw the recessive genotype decrease and ultimately die out. Our second experiment was to determine just how much the death of the recessive individuals had an effect on the gene pool. We observed that the effect on the gene pool was much higher than it used to be because of the limited alleles in the gene pool. The recessive alleles died out much quicker because of this.
Discussion
Breeding Bunnies: Discussion Questions
1. What was your original hypothesis?
If we breed bunnies for 10 trials, then the recessive alleles will die out.
2. Based on your lab data, do you need to change your hypothesis? Explain.
Yes , because our hypothesis stated that after 10 trials recessive trait would die out, but after the 10 trials there were still 2 recessive alleles. More trials would need to be conducted for the recessive alleles to die out.
3. Compare the number of alleles for the dominant characteristic with the number of alleles for the recessive characteristic.
The number of dominant alleles remained the same while the number of recessive alleles slowly dwindled because the homozygous and heterozygous dominant bunnies had the tools to survive, while the homozygous recessive bunnies didn’t.
4. Compare the frequencies of the dominant allele to the frequencies of the recessive allele.
The frequencies were the same at the beginning but as the trials went on the number of recessive alleles dropped as did the frequency.
5. In a real rabbit habitat new animals often come into the habitat (immigrate), and others leave the area (emigrate). How might emigration and immigration affect the gene frequency of F and f in this population of rabbits? How might you simulate this effect if you were to repeat this activity?
If a new species of bunnies with a different type of fur immigrated, the rate of rabbits with no fur might dwindle. There is also the possibility that the species may be dominant over the sparse-haired bunnies, causing there to be less bunnies with no fur. To simulate the effect we would add another colored bead to simulate the new trait.
6. How do your results compare with the class data? If significantly different, why are they different?
Our data is similar to the classes data as the recessive genes nearly or fully dies out.
7. How are the results of this simulation an example of evolution?
This is an example evolution because if the recessive alleles die out then you could say that the bunnies evolved to the point where the cold winter won’t kill them anymore.
Conclusion
From this lab through our first experiment we can conclude that the number of f alleles would dwindle over time. However the the recessive alleles did not fully die out after 10 trials. This disproved our hypothesis that said it would die out in 10 trials. If we continued this experiment, the recessive alleles would eventually die out. With our second experiment we noticed how much a alleles dying had an effect on the overall gene pool because of the small number of total alleles. It confirmed our hypothesis of extinction within the first 5 trials, because of the higher effect on the gene pool.
Citations
PBS. PBS. Web. 4 Feb. 2015. <http://www.pbs.org/wgbh/evolution/educators/lessons/lesson4/act1.html>.
"LabBench." LabBench. Web. 4 Feb. 2015. <http://www.phschool.com/science/biology_place/labbench/lab8/intro.html>.
Web. 4 Feb. 2015. <http://www-tc.pbs.org/wgbh/evolution/educators/lessons/lesson4/4_bunnies_data.pdf>.
Web. 4 Feb. 2015. <http://www-tc.pbs.org/wgbh/evolution/educators/lessons/lesson4/4_bunnies_quest.pdf>.