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Simulating Hardy-Weinberg Effects on Evolution Integrated Science 4 5/13 Name: Per: Background Understanding natural selection can be confusing and difficult. People often think that organisms consciously adapt to their environments. For example, that the peppered moth can change its color, the giraffe can permanently stretch its neck, the polar bear can turn itself white – all so that they can better survive in their environments. In reality, populations of organisms, not the individuals, adapt and evolve over time under the influence of natural selection and genetic drift. In this lab, you will use fish crackers to help further your understanding of measuring evolutionary change using allele frequencies and genotype frequencies, which together reflect the genetic make-up of a population. In addition, you will simulate the Hardy-Weinberg conditions and practice using the HardyWeinberg mathematical equations to determine if evolution has occurred over time. Hardy-Weinberg Conditions: 1. large population, 2. random mating, 3. no mutation, 4. no migration, 5. no selection Hardy-Weinberg Mathematical Equations: p + q = 1 and p2 + 2pq + q2 = 1 Basically, the Hardy-Weinberg equation describes the status quo. If the five conditions are met, then no change will occur in either allele or genotype frequencies in the population. The value of this type of model is that it provides a yardstick by which changes in allele frequency, and therefore evolution, can be measured. One can look at a population and ask: Is evolution occurring with respect to a particular gene allele? Facts About The Fish In this simulation, goldfish crackers are the natural prey of the terrible fish-eating shark – YOU! Fish come with two phenotypes: gold and white - The allele for gold color is recessive, so fish that have this phenotype are homozygous recessive for this gene (ff). - The allele for white color is dominant, so fish that have this phenotype are either homozygous dominant (FF) or heterozygous (Ff) for this gene. New fish are born every year and the birth rate equals the death rate. Births are simulated by reaching into the “ocean” of spare fish and randomly choosing the replacement fish. Hypothesis Read through the simulations first. Based on the simulations and the reading above, predict how allele frequencies (p and q) will be affected by each of the following: If no selection occurs, then… If selection occurs due to a homozygous recessive disadvantage (selected against), then… If genetic drift occurs due to a small population, then… Simulation 1: The Effects of No Selection Part A. Team Data for No Selection 1. Randomly choose a study population of 20 fish from the ocean. Note: there are equal numbers of gold and white fish in the ocean. 2. Count gold and white fish in the initial population of 20 and record your individual data for Generation 1 in Data Table 1. 3. From your initial population of 20 fish, randomly choose 6 and eat them. 4. Recall that the birth rate equals the death rate, so “give birth” to 6 new fish, by randomly choosing 6 from the “ocean”. 5. Count gold and white fish in the population for the second generation and record your data for Generation 2 in Table 1. 6. Repeat procedures 3 through 5 for Generations 3, 4, 5 and 6 (final). Remember, for each generation, eat randomly, replace randomly and record all data in Table 1. Data Table 1: No Selection - Team Data # of White Fish Generation # of Gold Fish 1 (initial) 2 3 4 5 6 (final) Part B. Class Data for No Selection 1. Determine the total number of white colored fish and the total number of gold colored fish in Generation 1 for your entire class. Record these values in Table 2. 2. Determine the total number of white colored fish and the total number of gold colored fish in Generation 6 for your entire class. Record these values in Table 2. 3. Using the Hardy-Weinberg Mathematical equations, calculate allele frequencies (p and q) and genotype frequencies (p2, 2pq and q2) of fish color for Generation 1 and Generation 6 for the entire class population. Show your work below and record the gene frequencies for the initial and final Instructions for Calculating Frequencies: To determine the frequency of the gold genotype (q2, homozygous recessive individuals), divide the number of gold individuals in the population by the total number of fish in the population. Once q2 is determined, calculate q (recessive alleles), then p (dominant alleles), and then 2pq (heterozygous individuals) and p2 (homozygous recessive individuals). populations in Table 2. Round all decimal values to the hundredths place. Data Table 2: No Selection - Class Data Generation 1 (initial) 6 (final) # of White Fish # of Gold Fish p q p2 2pq q2 No Selection - Class Data Initial Generation Calculations No Selection - Class Data Final Generation Calculations Simulation 2: The Effects of Selection Part A. Team Data for Selection 1. Randomly choose a study population of 20 fish from the ocean. Note: there are equal numbers of gold and white fish in the ocean. 2. Count gold and white fish in the initial population of 20 and record your individual data for Generation 1 in Table 3. 3. To simulate selection, the predator will no longer eat randomly. You, the terrible fish-eating sharks, much prefer to eat the gold colored fish. You will eat ONLY gold colored fish unless none are available, forcing you to eat white fish in order to survive. So… eat 6 gold colored fish if they are available in your initial generation. If not, supplement with white. 4. Recall that the birth rate equals the death rate, so “give birth” to 6 new fish, by randomly choosing 6 from the “ocean”. 5. Count gold and white fish in the restored population and record your data for Generation 2 in Table 3. 6. Repeat procedures 3 through 5 for Generations 3, 4, 5 and 6 (final). Remember, for each generation, eat selectively, replace randomly and record all data in Table 3. Data Table 3: Selection - Individual Data Generation # of White Fish # of Gold Fish 1 (initial) 2 3 4 5 6 (final) Part B. Class Data for Selection 1. Determine the total number of white colored fish and the total number of gold colored fish in Generation 1 for your entire class for the selection simulation. Record these values in Table 4. 2. Determine the total number of white colored fish and the total number of gold colored fish in the Generation 6 for your entire class for the selection simulation. Record these values in Table 4. 3. Using the Hardy-Weinberg Mathematical equations, calculate allele frequencies (p and q) and genotype frequencies (p2, 2pq and q2) of fish color for the Generation 1 and Generation 6 for the entire class population. Show your work below and record the gene frequencies for the initial and final populations in Table 4. Round all decimal values to the hundredths place. Data Table 4: Selection - Class Data Generation # of White Fish # of Gold Fish p q p2 2pq q2 1 (initial) 6 (final) Selection – Class Data Initial Generation Calculations Selection – Class Data Final Generation Calculations Simulation 3: The Effects of Genetic Drift Part A. Team Data for Genetic Drift 1. Randomly choose a study population of 6 fish from the ocean. Note: there are equal numbers of gold and white fish in the ocean. 2. Count gold and white fish in the initial population of 6 and record your individual data for Generation 1 in Table 5. 3. From your initial population of 6 fish, randomly choose 2 and eat them. 4. Recall that the birth rate equals the death rate, so “give birth” to 2 new fish, by randomly choosing 2 from the “ocean”. 5. Count gold and white fish in the population for the second generation and record your data for Generation 2 in Table 5. 6. Repeat procedures 3 through 5 for Generations 3, 4, 5 and 6 (final). Remember, for each generation, eat randomly, replace randomly and record all data in Table 5. Data Table 5: Genetic Drift - Individual Data Generation # of White Fish # of Gold Fish 1 (initial) 2 3 4 5 6 (final) Part B. Class Data for Genetic Drift 1. Determine the total number of white colored fish and the total number of gold colored fish in Generation 1 for your entire class for the selection simulation. Record these values in Table 6. 2. Determine the total number of white colored fish and the total number of gold colored fish in the Generation 6 for your entire class for the selection simulation. Record these values in Table 6. 4. Using the Hardy-Weinberg Mathematical equations, calculate allele frequencies (p and q) and genotype frequencies (p2, 2pq and q2) of fish color for the Generation 1 and Generation 6 for the entire class population. Show your work below and record the gene frequencies for the initial and final populations in Table 6. Round all decimal values to the hundredths place. Data Table 6: Genetic Drift - Class Data Generation # of White Fish # of Gold Fish p q p2 2pq q2 1 (initial) 6 (final) Genetic Drift – Class Data Initial Generation Calculations Genetic Drift – Class Data Final Generation Calculations Graphs 1. Prepare a graph of the class results that represents the effects of no selection on the allele frequencies (p and q) of the initial and final populations. 2. Prepare a graph of the class results that represents the effects of selection on the allele frequencies (p and q) of the initial and final populations. 3. Prepare a graph of the class results that represents the effects of genetic drift on the allele frequencies (p and q) of the initial and final populations. Discussion 1. Reflect on each hypothesis, and state whether each was supported or refuted. Explain why using data values to support your conclusion. a. No Selection: b. Selection: c. Genetic Drift: 2. What five conditions must exist for gene frequencies to stay the same over time? 3. What process occurs when there is a change in gene frequencies over long periods of time? 4. Explain what would happen if conditions changed and the recessive trait offered a selective advantage (was selected for rather than against)? 5. What would happen if it were more advantageous to be heterozygous? Would there still be homozygous fish in the population over time? Explain. Conclusion 6. Design an experiment to show how one of the following effects allele frequencies: a) migration, b) isolation, c) mutations. Attach additional paper as needed.