Evolution in a Fishbowl PDF

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UF BSC2005 Biology Written Assignment...

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Yvonne Le BSC2005 Spring 2021 Dr. Nicole Gerlach 02-25-2021

Module 7: Evolution in a Fishbowl Q1: Phenotypes The three genotypes for the koi RR, Rr, rr. The genotype RR corresponds to a solid red or deep orange color, Rr corresponds to a mottled orange and white, and rr corresponds to solid white. This is a codominant trait, because the heterozygous offspring express the phenotypes of both homozygous dominant and homozygous recessive traits. Q2: Simulation 1 Results At the end of simulation 1, the population size was 196, the allele frequencies were: R allele = 0.62, r allele = 0.38; and the genotype frequencies were: rr = 0.15, Rr = 0.46, RR = 0.39. Q3: Simulation 1 HWE The genotypes of your population at the end of Simulation 1 are in Hardy-Weinberg equilibrium, and are not close. This can be concluded by utilizing the given formula, which is RR^2 + 2Rr + rr^2 should equal 1, meaning (0.39)^2+2(0.46)+(0.15)^2 is what is being calculated. This results in 1.0946, which is close to 1. Q4: Simulation 1 Evolution Evolution has not occurred over the course of 100 generations in the Simulation 1 population. This can be concluded because the allele frequency remained constant throughout the simulation, hovering around 0.6 and 0.7, meaning that the dominant trait remained almost double the frequency of the recessive trait. Q5: Simulation 2 Results The parameter changed in simulation 2 was the mutation rate of “R to r” from 0 to 0.005. At the end of Simulation 2, the population size was 195, the allele frequencies were: R allele = 0.76, r allele = 0.24; and the genotype frequencies were: rr = 0.03, Rr = 0.42, RR = 0.55. Q6: Simulation 2 HWE According to the Hardy-Weinberg equilibrium equation, RR^2 + 2Rr + rr^2 should equal 1. After plugging in the data values and calculating (0.55)^2+2(0.42)+(0.03)^2, the result is 1.1434, which is close to 1. Therefore, the population in Simulation 2 was in Hardy-Weinberg equilibrium. Q7: Simulation 3 Alleles No, neither allele was lost from Simulation 3 after 200 generations. Q8: Simulation 4 Alleles No, neither allele was lost from Simulation 4 after 200 generations.

Q9: Population Size The results from Simulations 3 & 4 reflect that a smaller population size is more susceptible to genetic drift. There were wild fluctuations in the allele frequency x time graph for Simulation 3, while the one for Simulation 4 was relatively linear. These waves in Simulation 3 indicate random, drastic, and quick changes within the population. This may occur because smaller populations have fewer alleles to balance out sudden or random changes, such as a mutation. Even if only a few are affected or reproduced from this change, it may constitute a significant percentage within the population; enough to spread the trait to the majority of the population. Whereas in a large population, there are more alleles of each genotype, therefore a few being mutated or changed is still considered few and insignificant compared to the total number in the large population. Q10: Simulation 5 Fitness The fitness setting of 0.2 for rr in Simulation 5 means that the relative fitness of the recessive genotype is only one-fifth of the most fit genotype. In this simulation, both the RR and Rr genotypes have a relative fitness of 1, meaning they are the fittest genotype, and rr is only one-fifth as fit as the other two. This could also lead to the rr genotype, and the r allele, being the rarest due to their lesser ability to survive and reproduce. Q11: Simulation 5 Alleles The allele frequencies were: R allele = 0.85, r allele = 0.15; and the genotype frequencies were: rr = 0, Rr = 0.29, RR = 0.71. Neither allele disappeared from the population, but the rr genotype did disappear and the Rr genotype became increasingly rare, therefore the r allele was closest to disappearing. Q12: Simulation 6 Fitness This setting means that rr is the fittest genotype while Rr and RR are both only one-fifth as fit. The result of this is an overpopulation of rr genotype fish, and the Rr and RR genotypes, as well as the R allele, become increasingly rare due to their lack of fitness compared to that of the rr genotype. Q13: Simulation 6 Alleles The allele frequencies were: R allele = 0, r allele = 1; and the genotype frequencies were: rr = 1, Rr = 0, RR = 0. The R allele disappeared from the population. Q14: Genetic Disorders Even though the genotype for a homozygous recessive allele may disappear, the allele can still be present in a heterozygous genotype. And if two heterozygous genotypes pair and produce offspring, they have a 25% chance of producing one with a homozygous recessive genotype, thus recessive genetic disorders may still exist despite natural selection....