Lab 1 - PopGen I

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Texas A&M University, Corpus Christi *

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Biology

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Apr 3, 2024

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Population Genetics I Data Sheet Lab Activity 1 How did the PTC taste? similar to the paper What is your possible genotype? q^2 How did the thiourea taste? pretty bland but a little bit more tangy than the previous one. What is your possible genotype? p^2+2pq How did the sodium benzoate taste? similar to paper What is your possible genotype? q^2 Table 1-1 —Class data. You Number of Tasters Number of Non-tasters Total Students Thiourea No 14 10 24 Sodium benzoate Yes 20 4 24 PTC No 11 13 24 Table 1-2 —Phenotypic and allelic frequencies of tasters and non-tasters for PTC. Phenotype Allelic Frequency Tasters (p 2 +2pq) Non-tasters (q 2 ) p q Thiourea Class (obs) 0.826111 0.173889 0.583 0.417 Sodium benzoate Class (obs) 0.972111 0.027889 0.833 0.167 PTC Class (obs) 0.706236 0.293764 0.458 0.542 Class (exp) 11 13 .458 .542 1 Revised Fall 2023

How do the frequencies for the class compare with the frequencies for the North American population? There was not a big difference between the nontasters frequencies of the PTC in North America and the nontasters of the PTC in the class. However, there are more non tasters of PTC in North America than in the class. Is the class in Hardy-Weinberg equilibrium? No because the Hardy-Weinberg equilibrium classifies a population, our class only has 24 people in it. There is not enough data to determine if the class size has met all the Hardy-Weinberg equilibrium requirements. Although about 55% of the full North American population are PTC tasters, approximately 70% of the North American Caucasian population are tasters. If the class frequencies do not match the expected values for the overall population, what other factor(s) might contribute to the discrepancy? Population size. The overall population is greater in number and diversity than a class of 24 people. Diversity allows for natural selection and evolution to occur, but with a low rate of diversity among 24 people, this is limited and will affect expected values of frequencies. Example The ability to taste PTC is due to a dominant allele, T. Suppose 120 students conducted the taste test. Eighty-four tasted PTC, and thirty-six could not. Calculate the frequencies of T and t as follows: Because the genotypic frequencies of the population are unknown, we must assume the population is in Hardy-Weinberg equilibrium in order to calculate allelic frequencies. Since the frequency of (tt) = q 2 = 36/120 = 0.30, then the square root of q 2 will give us q. √ ❑ Since q = 0.547, then p = 1-0.547 = 0.453 Given that p = 0.453 and q = 0.547; The frequency of (TT) = p 2 = 0.453 2 = 0.205 2 Revised Fall 2023

The frequency of (Tt) = 2pq = 2 (0.453)(0.547) = 0.496 The frequency of (tt) = q 2 = 0.547 2 = 0.30 Given these frequencies, and assuming the population is in Hardy-Weinberg equilibrium, we expect the following genotypes in the population of 120 students: TT = 0.205(120) = 25 students Tt = 0.496(120) = 59 students tt = 0.30(120) = 36 students Lab Activity 3 Table 1-3. Habitat Mutation (Y/N) Predation (Y/N) Time (Months) Fur Color frequency Genotype frequencies Allele frequencies Field N N 120 Light: 22% Medium: 62% Dark: 17% RLRL - 21% RLRD - 10% RDRL - 46% RDRD - 23% RL - 53% RD - 47% RESET Field N Y 120 Light: 0% Medium: 0% Dark: 100% RLRL - 0% RLRD - 4% RDRL - 10% RDRD - 86% RL - 2% RD - 98% RESET Field Y N 120 Light: 20% Medium: 50% Dark: 30% RLRL - 35% RLRD - 18% RDRL - 24% RDRD - 22% RL - 56% RD - 44 % Beach Y N 400 Light: 25% Medium: 54% Dark: 21% RLRL - 83% RLRD - 6% RDRL - 11% RDRD - 0% RL - 91% RD - 9% Lab Activity 3 Questions: 1. Examine your data. Comparing your first two populations, with and without predation, how did predation influence the population? 3 Revised Fall 2023

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