Assignment 1A - Exploring Evolution with SIMBIO Sickle Cell Allele Exercise PDF

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Exploring Evolution with SIMBIO Sickle Cell Allele Exercise...

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A107 Assignment 1a: Exploring Evolution with SIMBIO Sickle Cell Allele Exercise ANSWER SHEET template (to use this sheet, rename it with your own name, type your answers after each question, save as a document or pdf and upload it as a single attachment into OnCourse Assignments.) YOUR NAME HERE: Exercise A: A4.1 When the HbS allele goes up, what happens to the HbA allele? The hbA allele goes down A4.2 What do the two allele frequencies add up to? The two allele frequencies must add up to 1 or 100% A5.1 What is the frequency of the sickle-cell allele? .10 A5.2 What is the frequency of the normal hemoglobin allele? .80 A5.3 How many malaria deaths were there in the past 5 years? 25 A5.4 How many sickle-cell deaths were there in the past five years? 64 A6.1 What happened to the allele frequencies and number of deaths? The allele frequencies of the hbS allele decreased at a constant rate, while the hbA allele increased constantly. The number of deaths from malaria decreased to 0, which the sickle cell anemia decreased to 4.

Exercise B: B1.1 Where do you think you’ll find that the most villagers are dying from sickle-cell anemia? Explain. These villagers will be found where many mosquitoes are present or in areas that are considered to be wet regions because people with sickle cell anemia won’t have malaria in that environment. B1.2 Do you think the sickle-cell allele will disappear in any of your runs for the different regions? Explain. Yes, I think the sickle cell allele will disappear due to the limited number of mosquitoes in dry areas. In this case natural selection won’t favor sickle cell since there’s little risk of malaria exposed in the dry environment. B2.1

Very wet Wet Slightly wet Dry

Number of malaria deaths (5 yr) 22 36 30 0

Frequency % of HbA 37% 51% 8% 78%

Number of sickle cell deaths (5 yr) 54 27 7 7

B2.2 What happened to the frequency of the sickle-cell allele as you decreased the malaria death rate? The frequency of the sickle cell allele decreased. B2.3 Were your predictions in 1.1 and 1.2 correct? Explain. I was partially correct because dry regions decrease the number of sickle cell anemia deaths, and high death rates will be found in the wet regions. However, I was wrong when I said that the allele would completely disappear because they did not. B2.4 As the malaria death rate decreased, what happened to the number of sickle cell deaths? Sickle cell deaths and malaria decreased. B2.5 As you decreased the malaria death rate, what do you think happened to the proportion of villagers with the HbA/HbA genotype? Explain. The villagers with hbA/hbA genotype would increase since the threat of malaria is gone. As a result, sickle cell carriers/ deaths would decrease because hemoglobin homozygotes will survive and pass traits. In other words, the offspring has a chance to die of sickle cell.

Exercise C: C2.1 Why did the HbS allele pattern vary from run to run? C3.1

Trial 1 2 3 4 5 6 7 8 9 10

Malaria death rate = 0.05 Did the HbS allele disappear? No Yes Yes No Yes Yes Yes Yes Yes No

Malaria death rate = 0.2 Did the HbS allele disappear? No No No Yes No No No No Yes No

C4.1 In which environment do you think the sickle cell allele was most likely to have become established first? Explain. Sickle cell allele was most likely to have become established in wet regions where many mosquitoes are present. This is because a wet environment supports the components that spread the hbS allele. C4.2 Describe how your hypothesis in C4.1 fits with information about the distribution of other genetic anti-malarials described in your readings. Sickle cell anemia thrives in wet environments and individuals who have sickle cell anemia will not be affected by malaria. However, individuals who do not carry the sickle cell anemia will be affected by malaria.

Exercise D: D2.1 Calculate and record the allele frequencies : Village Size Small Medium Large

Frequency % of HbS 3 1 .63

Frequency % of HbA 1 2 .57

D3.1 Which village has the most consistent allele frequencies from run to run? Large village D3.2 Which village has the most variable allele frequencies? Middle village D4.1 Do you think that decreasing the initial frequency of the HbS allele to 0.1 will increase the chance of that allele disappearing? Explain. Yes, less frequent means it will be less likely to spread. D5.1 Was your prediction in D4.1 correct? Yes D5.2 Did the HbS allele consistently disappear from all the villages? No D5.3 Which village was influenced the least by genetic drift? Large villages

Exercise E: E1.1 How have current distributions of the sickle cell trait been influenced by gene flow? (Answer in a paragraph or two, using examples from the readings.) The current distributions of the sickle cell trait have been influenced by gene flow in many places around the world. The article discusses how sickle cell trait has been discovered in places such as Asia, Africa, and central and north America. We were able to learn that in order for sickle cells anemia to be present, malaria does not have to be present and the gene will still be able to survive throughout generations where the gene of the sickle cell was once very populated and then migrated through families throughout years. E1.2 How could medical interventions influence the future incidence of sickle cell anemia in the United States? (Answer in a paragraph or two, using examples from the readings.) Medical interventions can influence the future incidence of sickle cell anemia in the united states because doctors have made discoveries that will be able to treat people who contain sickle cell anemia around the globe. It’s rare to find an individual who contains this trait in the US today since malaria is currently not present and the cell is passed through reproduction. However, doctors have found treatments making lower death rates allowing an increase in the sickle cell allele.

E2.1 Explain how you think changing factors are likely to influence the future incidence of sickle cell trait in the U.S. (Answer in a paragraph or two, using examples from the readings.) A changing factor that would likely influence the future incidence of sickle cell traits in the U.S. could be a cure that decreases the death rate of the sickle cell anemia. In this case, due to reproduction, the allele would become more common. On the other hand, due to the decrease of malaria, having the sickle- cell allele would not be so beneficial. Therefore, natural selection could get rid of the gene over time.

E3 Design and run an experiment using this simulation model to test some of the predictions you describe in E1&2 above. Describe your experiment and your results. (Answer in a paragraph or two, using examples from the readings.) I ran an experiment to determine my prediction in regard to whether or not sickle- cell anemia is still fatal now that there is modern medicine. In conclusion, I learned that my predictions were accurate since the lack of selective pressure affected

the allele to stay stable because of random mating. During the experiment, it came to my attention that the 5 populations varied in their frequencies of the A allele. For example, some populations slowly got close to 1, but never hit it, while others quickly rose to 1....