Advanced Placement Lab 2 EDVO-Kit # Population Genetics and Evolution Storage: Store entire experiment at room temperature. EXPERIMENT OBJECTIVE The objective of this experiment module is to use the Hardy-Weinberg theorem to calculate allele and genotype frequencies. Students will predict the effect of selection processes on allelic frequencies, and discuss the effect of changes in allelic frequencies on evolution. EDVOTEK, Inc. 1-00-EDVOTEK www.edvotek.com EVT 0011AM
2 EDVO-Kit # 2 Table of Contents Page Experiment Components 3 Experiment Requirements 3 Background Information 4 Experiment Procedures Experiment Overview 6 Part A 7 Part B 9 Part C 13 Part D 17 Part E 19 Instructor's Guidelines Notes to the Instructor 21 Pre-Lab Preparations 22 Expected (SAMPLE CASE) Results and Selected Answers 23 Material Safety Data Sheets 26 Advanced Placement () Program is a registered trademark of the College Entrance Examination Board. These laboratory materials have been prepared by EDVOTEK, Inc. which bears sole responsibility for their contents. EVT 0011AM 1-00-EDVOTEK www.edvotek.com
EDVO-Kit # 2 3 Experiment Components This experiment is designed for 10 lab groups PTC taste paper Control taste paper Storage: Store entire experiment at room temperature. Requirements Calculator with square root function 100 index cards - 3 x 5 All components are intended for educational research only. They are not to be used for diagnostic or drug purposes, nor administered to or consumed by humans or animals. EDVOTEK, The Biotechnology Education Company, and InstaStain are registered trademarks of EDVOTEK, Inc. EDVOTEK - The Biotechnology Education Company 1-00-EDVOTEK www.edvotek.com FAX: (301) 340-052 email: edvotek@aol.com EVT 0011AM
4 EDVO-Kit # 2 Population genetics deals with analysis of gene frequencies in a population over many generations. The concept of describing frequencies of inherited traits owes its origin to scientific works published at the beginning of the 20th century. A 190 paper, Mendelian Proportions in a Mixed Population published in Science 2 (49-50) by British mathematician G.H. Hardy, and a separate independent study also published in 190 by the German physician W. Weinberg, both suggested that gene frequencies were not dependent upon dominance or recessiveness but may remain unchanged from one generation to the next under a set of idealized conditions. These classic papers describe an equation which has come to be called the Hardy-Weinberg theorem of genetic equilibrium. This theorem has become the basis for population genetics. Background Information The Hardy-Weinberg theorem is used to determine the frequencies of individual alleles of a pair of genes, and the frequency of heterozygotes and homozygotes in the population. The theorem states that in the absence of outside forces such as mutation, selection, random genetic drift, and migration, gene frequencies remain constant over many generations in a large population. It is important to remember that in natural populations, events such as gene mutation, selection of genotypes which confer enhanced viability, presence of lethal homozygous recessive genes, nonrandom mate selection, and immigration and emigration of individuals of a population, are events that do occur. Nevertheless, the Hardy-Weinberg theorem is useful since unexpected deviations can point to the occurrence of evolutionary significant events such as speciation. Distribution frequencies of two alleles for a given gene at a single locus, one being dominant, the other recessive, will follow a binomial distribution in the population. Consider the case of two alleles for a gene, one dominant and the other recessive. Let p = the frequency of one allele and q = the frequency of the other. If gene frequencies are expressed as decimals, the following must be true, Equation # 1: p + q = 1 and, Equation # 1a: p = 1 - q therefore, Equation # 2: (p + q) 2 = 1. Expanding equation #2 generates, Equation #3: p 2 + 2pq + q 2 = 1. 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Background Information EDVO-Kit # 2 5 When equation 3 is applied to an ideal population, it follows that the frequency of homozygous dominant individuals is p 2, the frequency of the heterozygotes is 2pq, and the frequency of homozygous recessives is q 2. As an example, consider the following hypothetical situation. The famous European geneticist Professor Ed V. Otek, tested his rather large genetics class for the ability to taste the chemical phenylthiocarbamide, PTC. He knew that the gene for this ability to taste PTC had two alleles, the dominant allele for tasting called T, and the recessive allele called t. He found that out of 1000 students, there were 700 students with the ability to taste PTC and 300 who lacked the ability to taste PTC. He used the Hardy- Weinberg equation to determine the gene frequencies for the T and t alleles of the gene for the ability to taste PTC. His notes show the following analysis: A Converted raw data to decimals. Frequency of two genotypes for tasting, TT and Tt, was 700/1000 = 0.7. Frequency of genotype for inability to taste PTC, t t, was 300/1000 = 0.3. B Determined gene frequency of the unique allele. From the Hardy-Weinberg equation # 3, (p 2 + 2pq + q 2 = 1), the frequency of non-tasters, tt = 0.3 = q 2. Taking the square root of 0.3, q = 0.5477, and 0.5477 is the frequency of the t allele in Dr. Otek s student population. C Determined gene frequency of other allele, p: From equation # 1a, (p = 1-q), the frequency of p is 0.4523. D. Determined frequency of homozygous TT and heterozygous Tt individuals in the population. Using equation #3: p 2 + 2pq + q 2 = 1, (0.4523) 2 + 2(0.4523 x 0.5477) + (0.5477) 2 = 1 The frequency of homozygous tasters is, TT = p 2 = 0.4523 2 = 0.2046. The frequency of heterozygous tasters is Tt = 2pq = 2 (0.4523 x 0.5477) = 0.4954. During this experiment students will utilize the Hardy-Weinberg equation to analyze population data from the class. 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
6 EDVO-Kit # 2 Experiment Overview EXPERIMENT OBJECTIVE To use the Hardy-Weinberg theorem to calculate allele and genotype frequencies. To predict the effect of selection processes on allelic frequencies and discuss the effect of changes in allelic frequencies on evolution. WORKING HYPOTHESIS Experiment Procedure If there is no selection for any allele in a large randomly-mating population, then the gene frequencies will remain constant over many generations. However, if there are outside forces such as selection for an allele, heterozygote advantage, and genetic drift working in a population, then the gene frequencies will change over time. LABORATORY SAFETY Remember to wear gloves and safety goggles during all hands-on laboratory activities. Always wash hands thoroughly with soap and water after handling reagents or biological materials in the laboratory. MATERIALS FOR THE EXPERIMENT Each Lab Group should have the following materials: PTC taste paper Control taste paper Index cards - 3 x 5 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Experiment Procedure EDVO-Kit # 2 7 Part A: Student Experimental Procedures ESTIMATION OF GENE FREQUENCIES FOR THE TRAIT TO TASTE PTC WITHIN A SMALL SAMPLE POPULATION. This experiment deals with the determination of the gene frequency of a human trait amongst students with no known selective advantage. The ability to taste the chemical phenylthiocarbamide, PTC, is one such human trait. The ability to taste PTC is due to the presence of a dominant allele, T. Therefore, all tasters will either be homozygous, TT, or heterozygous, Tt. Non-tasters will be homozygous for the recessive gene, tt. Using the Hardy-Weinberg equation #3, first determine the frequency, q 2, of the homozygous recessive gene t, which is directly determined from your class data. The frequency of the non-taster phenotype in your class equals the frequency of the genotype tt. q is determined as the square root of the frequency of non-tasters. Using equation # 1a, the value of p is determined by subtraction. We begin this analysis using the frequency of the homozygous recessive, since for this experiment it is impossible to determine whether the true genotype of the tasters is either TT or Tt. 1. Students groups should obtain a PTC taste strip and a control strip. 2. Every member of the group should first taste the control strip of paper. 3. Every person should taste the PTC impregnated strip of paper. Compare the taste of the control and the PTC paper. If you are a taster, the PTC paper strip will be bitter. Non-tasters will not notice a difference between either strip of paper. 4. For the class, record the total number of tasters and the total number of non-tasters on the blackboard. 5. Determine decimal value by division for tasters (p 2 + 2pq), and likewise the decimal value for non-tasters (q 2 ). For example, there are 100 people in your class. 25 are nontasters and 75 are tasters. Then 25/100, or 0.25, is the frequency of non-tasters, and 75/100, or 0.75, is the frequency of tasters. 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
EDVO-Kit # 2 Part A: Student Experimental Procedures 6. Record your values in Table 1. Use Hardy-Weinberg as described above to determine the value of p and q for your class. TABLE 1: Phenotypes and Gene Frequencies for Trait to Taste PTC CLASS PHENOTYPES ALLELE FREQUENCY CALCULATED BY THE HARDY WEINBERG EQUATION % TASTERS % NON-TASTERS p 2 + 2pq q 2 p q Experiment Procedure Part A: Study Questions CLASS POPULATION NORTH AMERICAN POPULATION 0.55 0.45 Answer the following study questions in your laboratory notebook or on a separate worksheet. 1. What is the frequency of homozygous tasters, p 2, in your classroom? 2. What is the frequency of heterozygous tasters, 2pq, in your classroom? 3. What is the frequency of homozygous non-tasters in your classroom? 4. Determine the percentage of the three genotypes TT, Tt, and tt in your classroom. Hint: multiply the values obtained for question 1, 2, and 3 by 100. 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Experiment Procedure EDVO-Kit # 2 9 Part B: Student Experimental Procedures TESTING AN IDEALIZED HARDY-WEINBERG POPULATION WITHOUT SELECTION For this example, we will consider the class to be a natural randomly mated group with no selection and each individual being heterozygous for a particular phenotype having the genotype A. The initial gene frequency in this population is 0.5 for A, the dominant allele, and 0.5 for a, the recessive allele. Therefore p and q both equal 0.5. Every pair of individuals should keep track of their child s genotype after each mating. In addition, the class as a group must keep track of totals for each mating during each of five (5) generations. 1. Work in pairs. For each generation, each pair will produce two offspring. 2. For this example, each person in the class should obtain 4 index cards. Label two A and two a. These cards represent the only two unique gametes which a heterozygous individual with a genotype of Aa can produce. You have 4 cards since there are two cell divisions during meiosis. 3. Each person in a group should place the index cards face down on lab bench. Shuffle cards so that they are randomly mixed. Each person selects only one card from their pile of 4 cards, and places it together with one selected by their partner. 4. Flip the cards over and record the genotype of this mating in Table 2. TABLE 2: Hardy-Weinberg Population GENERATION NUMBER 1 2 3 OFFSPRING GENOTYPE AA, Aa, or aa CLASS TOTALS FOR EACH GENOTYPE AA Aa aa 4 5 CLASS TOTALS FOR EACH GENOTYPE ADDED OVER 5 GENERATIONS 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
10 EDVO-Kit # 2 Part B: Student Experimental Procedures 5. Recover your index card so again you have two of each allele A, and a. Reshuffle the cards between selections. 6. With your partner, produce a second offspring and record the genotype. Be sure to collect the class totals on the blackboard at the end of this generation and for the next 4 generations. 7. Now you will assume the genotype of the first child and your partner will assume the genotype of the second child.. Re-label your four index cards to reflect the gametes which you would produce with the new genotype. For example if your child was AA, your cards would be labeled A,A,A,A. Similarly, if your child was Aa, your cards would be labeled A,A,a,a. Experiment Procedure 9. Now randomly select a different partner in your class. 10. Using the same procedure for the first generation, produce two new offsprings with your new mate. Again record the genotype of each child in the table. Remember, the class as a group should also keep track of each genotype after each generation. Record the class totals. 11. As before, one student of the pair will assume the genotype of the first child and the other student should assume the genotype of the second child produced during this mating. If necessary, relabel your index cards to reflect the four gametes which you would produce. 12. Again, each person should randomly seek out another mate and repeat the procedure generating two new children. Record the new genotypes as before. Keep track of the class totals after each mating. 13. This process of random mating without selection should continue until you have produced 5 generations of children. 14. Be sure to place your individual results and the class totals for each mating into Table 2. 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Experiment Procedure EDVO-Kit # 2 11 Part B: Study Questions STUDY QUESTIONS Answer the following study questions in your laboratory notebook or on a separate worksheet. 1. Using the total of all class data over the 5 generations considered as one large population, compute the genotypic frequency for each of the three possible genotypes. The class totals for each genotype should be summed over all of the 5 generations as indicated in Table 2. These three numbers, which are the bottom 3 cells in Table 2, should be added together to determine the grand total number of all individuals with genotypes, AA + Aa + aa in your class population. This number is used as the divisor for determination of the frequencies of the AA, Aa, and aa genotypes in the population after 5 generations. a. AA genotypic frequency = Total number of AA individuals Total number of all individuals in the population b. Aa genotypic frequency = Total number of Aa individuals Total number of all individuals in the population c. aa genotypic frequency = Total number of aa individuals Total number of all individuals in the population 2. Record your results of the actual class genotypic frequencies determined in question 1 above. a. AA (p 2 ) genotypic frequency b. Aa (2pq) genotypic frequency c. aa (q 2 ) genotypic frequency 3. Determine the theoretical Hardy-Weinberg frequencies of the beginning population when p = 0.5, and q =0.5. p 2 (AA) = 2pq (Aa) = q 2 (aa) = 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
12 EDVO-Kit # 2 Part B: Study Questions 4. From the data in question #3, determine q from q 2, and determine p. 5. Calculate the values of p and q in your class population for the 5th generation only. This represents the frequencies of the two alleles after 5 generations of totally random mating for a gene which does not confer any selective advantage. Use these p and q values to determine the gene frequencies with the Hardy- Weinberg equation #3, p 2 + 2pq + q 2 = 1. From Table 2, the total number of individuals in the 5th generation is obtained by summation across the last 3 cells in the row for the 5th generation, that is AA + Aa + aa (this should also be the same value as the number of students in your class!). Experiment Procedure a. AA genotypic frequency of the 5th generation = Total number of AA individuals in the 5th generation Total number of all individuals in the 5th generation b. Aa genotypic frequency of the 5th generation = Total number of Aa individuals in the 5th generation Total number of all individuals in the 5th generation c. aa genotypic frequency of the 5th generation = Total number of aa individuals in the 5th generation Total number of all individuals in the 5th generation d. Remember that you determine q as the square root of the value determined in 5c. Also p = 1 - q. Determine the following values for the 5th generation only; p 2 (AA) = 2pq (Aa) = q 2 (aa) = 6. How have the values of p and q changed? 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Experiment Procedure EDVO-Kit # 2 13 Part C: Student Experimental Procedures TESTING AN IDEALIZED HARDY-WEINBERG POPULATION WITH SELECTION A number of recessive alleles are lethal when they occur in homozygous aa individuals. These individuals usually do not survive until they are old enough to mate, or are unable to mate. Such a selection serves as a biological mechanism to remove the recessive allele a from the population. Only the AA, and Aa individuals survive to mate. Therefore, over many generations there is a gradual decline in frequency of the recessive a allele since the aa individuals do not service to mate. Consider the following example: Where p (A)= 0.5, and q (a) = 0.5, and genotypes AA, Aa, and aa are possible, p 2 + 2pq + q 2 = 0.25 + 0.50 + 0.25. If aa individuals are unable to mate, the new genotypic frequency would be: AA = 0.25/ (0.25 + 0.5) = 0.33 Aa = 0.5/ (0.25 + 0.5) = 0.67 The aa allele is eliminated from the calculation since it is unable to produce further offspring for the next generation. Therefore, the only possible matings are shown in Table 3. TABLE 3: Hardy-Weinberg Population with Selection Genotypic Frequencies Matings Frequencies AA Aa aa AA x AA (0.33) 2 = 0.11 AA x Aa 2 (0.33 X 0.67) = 0.22 0.22 Aa x Aa (0.67) 2 = 0.45 0.11 0.23 0.11 Total Population Genetic Frequencies 0.44 0.45 0.11 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
14 EDVO-Kit # 2 Part C: Student Experimental Procedures The frequency of the a allele has decreased to 0.33 (the square root of 0.11) after only 1 generation. With selection against the double recessive, the a allele is gradually eliminated from the population. The following equation will predict gene frequency of the recessive allele, q ( a ) after n, number of generations, with complete selection against the double recessive. q n = q o /(1 + nq o ) q n = the frequency of the recessive allele after n generations q o = the initial frequency of the recessive allele. Each pair of students should keep track of their child s genotype after each mating. In addition, the class as a group must record totals for each mating during each of the 5 generations. Experiment Procedure 1. Each student should begin with 4 index cards. Two labeled A, and two labeled a. Proceed in a manner similar to that of Part B with one slight difference. If you produce an aa offspring you must do the following: Record it in Table 4 for the class total. In this exercise you must mate again with the same partner until you produce either an AA or Aa offspring. Continue randomly mating for 5 generations and be sure to record your data. Reshuffle and reselect cards until you obtain either an AA or Aa child, keeping the population size constant. Record your individual results and class totals in Table 4. 2. Continue the procedure for 5 generations. TABLE 4: Hardy-Weinberg Population with Selection GENERATION NUMBER 1 2 3 OFFSPRING GENOTYPE AA, Aa, or aa CLASS TOTALS FOR EACH GENOTYPE AA Aa aa 4 5 CLASS TOTALS FOR EACH GENOTYPE ADDED OVER 5 GENERATIONS 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Experiment Procedure EDVO-Kit # 2 15 Part C: Study Questions Answer the following questions in your laboratory notebook or on a separate worksheet. 1. Calculate, from your experimental data, gene frequency values of the A, and a alleles, as well as p and q in your class population for the 5 th generation only. \This represents frequencies of two alleles after 5 generations of totally random mating for a gene in which recessive genotype aa is lethal. From Table 3, the total population in the 5th generation (which is used as the divisor below) is obtained by summation across the last 3 cells in the row for the 5 th generation, that is AA + Aa + aa. a. AA genotypic frequency of the 5 th generation = Total number of AA individuals in the 5th generation Total number of all individuals in the 5th generation b. Aa genotypic frequency of the 5 th generation = Total number of Aa individuals in the 5 th generation Total number of all individuals in the 5 th generation c. aa genotypic frequency of the 5 th generation = Total number of aa individuals in the 5 th generation Total number of all individuals in the 5 th generation d. Remember that you determine q as the square root of the value determined in 1c and p = 1- q. Determine the following values for the 5 th generation only; p 2 (AA) = 2pq (Aa) = q 2 (aa) = 2. How have values of p and q changed since the first generation? 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
16 EDVO-Kit # 2 Part C: Study Questions 3. As discussed above, the following equation can be used to predict the frequency of the recessive allele in the population when there is selection against the double recessive individuals. qn = q o / (1 + nq o ) qn = frequency of the recessive allele after n generations q o = the initial frequency of the recessive allele. a. Using this equation, predict frequency of the recessive allele after 1, 5, 10, and 100 generations. Assume an initial p = 0.5, and q = 0.5. b. How does the calculated value for the 5th generation compare to your experimental value for the 5 th generation? Experiment Procedure 4. Compare the values of p and q determined after 5 generations here with selection against the double recessive, to the value of p and q which you have already determined in Part B, after 5 generations without selection. 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Experiment Procedure EDVO-Kit # 2 17 Part D: Student Experimental Procedures TESTING AN IDEALIZED HARDY-WEINBERG POPULATION, WITH HETEROZYGOTIC ADVANTAGE It was easy to see in Part C that selection against the homozygous recessive lethal genotype results in a decrease in the original q value. However, it has been shown this is not always the case as in certain recessive alleles remain a high level. An example is the case of Sickle-cell anemia, common among individuals of African origin. In this disease, the heterozygote has an advantage over the homozygous dominant allele. Individuals who have heterozygotic genotype have an increased resistance to malaria which historically was deadly in Africa. This type of advantage is incorporated in the following simulation. 1. Keep everything the same as in Part C, except if the offspring is AA, flip a coin. The individual survives if the coin lands tails up; the individual does not survive if it lands heads up. 2. Simulate five generations, starting again with the initial genotype from Part B. The genotype aa will never survive. The homozygous dominant genotypes survive only if the coin toss comes up tails. In order to keep a constant population size, the same two parents must try again until they produce two surviving offspring. Obtain new allele cards from the pool as needed. Collect and record class genotypes in Table 5. Calculate the p and q frequencies. 3. If time permits, start with the F 5 genotype, go through five more generations, and total the genotypes. Calculate the frequencies of p and q. TABLE 5: Hardy-Weinberg Population with Heterozygotic Advantage GENERATION NUMBER 1 2 3 OFFSPRING GENOTYPE AA, Aa, or aa CLASS TOTALS FOR EACH GENOTYPE AA Aa aa 4 5 CLASS TOTALS FOR EACH GENOTYPE ADDED OVER 5 GENERATIONS 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
1 EDVO-Kit # 2 Part D: Study Questions Answer the following questions in your laboratory notebook or on a separate worksheet. 1. Compare the changes in p and q frequencies in Part C with Part B and Part D. Explain. 2. Will the recessive allele be completely eliminated in either Part C or Part D? Explain. 3. Why is heterozygote advantage important in maintaining genetic variation in a population? Experiment Procedure 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Experiment Procedure EDVO-Kit # 2 19 Part E: Student Experimental Procedures TESTING AN IDEALIZED HARDY-WEINBERG POPULATION, WITH GENETIC DRIFT Changes in a small gene pool is known as genetic drift. The simulation that follows incorporates this fact into the following simulation. 1. Divide the class into three isolated populations. Individuals from one isolated population will not mate with individuals from another population. 2. Go through five generations. Record the new genotypic frequencies. Calculate the new frequencies of p and q for each population. TABLE 6: Hardy-Weinberg Population with Genetic Drift GENERATION NUMBER 1 2 3 OFFSPRING GENOTYPE AA, Aa, or aa CLASS TOTALS FOR EACH GENOTYPE AA Aa aa 4 5 CLASS TOTALS FOR EACH GENOTYPE ADDED OVER 5 GENERATIONS 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
20 EDVO-Kit # 2 Part E: Study Questions Answer the following questions in your laboratory notebook or on a separate worksheet. 1. How do the initial genotypic frequencies of the populations compare? 2. Show a difference between small and large populations in allelic frequency? Explain. Experiment Procedure 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
EDVO-Kit # 2 21 Notes to the Instructor OVERVIEW OF LABORATORY INVESTIGATIONS The "hands-on" laboratory experience is a very important component of the science courses. Laboratory experiment activities allow students to identify assumptions, use critical and logical thinking, and consider alternative explanations, as well as help apply themes and concepts to biological processes. M o n Online Ordering now available www.edvotek.com Visit our web site for information about EDVOTEK's complete line of experiments for biotechnology and biology education. EDVO-TECH - Fri 9 SERVICE 1-00-EDVOTEK (1-00-33-635) am - 6 E T pm EDVOTEK experiments have been designed to provide students the opportunity to learn very important concepts and techniques used by scientists in laboratories conducting biotechnology research. Some of the experimental procedures may have been modified or adapted to minimize equipment requirements and to emphasize safety in the classroom, but do not compromise the educational experience for the student. The experiments have been tested repeatedly to maximize a successful transition from the laboratory to the classroom setting. Furthermore, the experiments allow teachers and students the flexibility to further modify and adapt procedures for laboratory extensions or alternative inquiry-based investigations. ORGANIZING AND IMPLEMENTING THE EXPERIMENT Class size, length of laboratory sessions, and availability of equipment are factors which must be considered in the planning and the implementation of this experiment with your students. These guidelines can be adapted to fit your specific set of circumstances. Technical Service Department Mon - Fri 9:00 am to 6:00 pm ET FAX: (301) 340-052 web: www.edvotek.com email: edvotek@aol.com Please have the following information: The experiment number and title Kit Lot number on box or tube The literature version number (in lower right corner) Approximate purchase date If you do not find the answers to your questions in this section, a variety of resources are continuously being added to the EDVOTEK web site. www. edvotek.com In addition, Technical Service is available from 9:00 am to 6:00 pm, Eastern time zone. Call for help from our knowledgeable technical staff at 1-00-EDVOTEK (1-00-33-635). Instructor's Guide 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
22 EDVO-Kit # 2 Pre-Lab Preparations 1. Each student group should receive the following: PTC tasting strips for each student Control taste strips for each student - 12 index cards 2. The experiment can be expanded to include several other Mendelian phenotypes, which also appear to lack any selective advantage. For example, students can measure the class frequency of free versus attached ear lobes. Free ear lobes are dominant, attached ear lobes are recessive. 3. Students may also use the Chi-square statistic to compare their classroom data with the average for North America. Instructor's Guide 1-00-EDVOTEK www.edvotek.com without the written consent of EDVOTEK, Inc. Copyright 1991, 1992, 1995, 1997, 199, 1999, 2003, 2004, 2005, 200 EDVOTEK, Inc., all rights reserved. EVT 0011AM
Please refer to the kit insert for the Answers to Study Questions
IDENTITY (As Used on Label and List) PTC taste paper Section I Manufacturer's Name EDVOTEK, Inc. Address (Number, Street, City, State, Zip Code) 14676 Rothgeb Drive Rockville, MD 2050 Material Safety Data Sheet May be used to comply with OSHA's Hazard Communication Standard. 29 CFR 1910.1200 Standard must be consulted for specific requirements. Section II - Hazardous Ingredients/Identify Information Hazardous Components [Specific Chemical Identity; Common Name(s)] OSHA PEL ACGIH TLV CAS # 103-5-5 Phenylthiourea, 1- Phenyl - 2 thiourea, Phenylthiocarbamide Note: Blank spaces are not permitted. If any item is not applicable, or no information is available, the space must be marked to indicate that. Emergency Telephone Number (301) 251-5990 Telephone Number for information (301) 251-5990 Date Prepared 0-19-05 Signature of Preparer (optional) Other Limits Recommended % (Optional) Section III - Physical/Chemical Characteristics Boiling Point NO data Specific Gravity (H 0 = 1) 2 NO data Vapor Pressure (mm Hg.) Vapor Density (AIR = 1) NO data NO data Melting Point Evaporation Rate (Butyl Acetate = 1) NO data NO data Solubility in Water Soluble Appearance and Odor paper strip Section IV - Physical/Chemical Characteristics Flash Point (Method Used) Flammable Limits LEL UEL NO data NO data NO data Extinguishing Media use media suitable to extinguish surrounding fire Special Fire Fighting Procedures Firefighters should wear full protective equipment and NIOSH breathing apparatus Unusual Fire and Explosion Hazards Thermal decomposition or contact with acids or acid fumes produces toxic fumes. Section V - Reactivity Data Stability Unstable Conditions to Avoid Stable X Heat, acid, or acid fumes Incompatibility Acids Hazardous Decomposition or Byproducts NOx, SOx Hazardous May Occur Conditions to Avoid Polymerization Will Not Occur X Heat, acid, or acid fumes Section VI - Health Hazard Data Route(s) of Entry: Inhalation? Skin? Ingestion? No Yes Yes Health Hazards (Acute and Chronic) Ingesting copious amounts of the chemical can be harmful or fatal. Carcinogenicity: NTP? IARC Monographs? OSHA Regulation? None No data No data No data Signs and Symptoms of Exposure Skin irritation. Ingesting copious amounts of the chemical will cause gastrointestinal discomfort. Medical Conditions Generally Aggravated by Exposure None noted Emergency First Aid Procedures Skin: Wash exposed area for 15 minutes. Seek medical attention if irritation persists. If copious amounts of the chemical are ingested, immediately call poison control center. Induce vomiting. Section VII - Precautions for Safe Handling and Use Steps to be Taken in case Material is Released for Spilled NA Waste Disposal Method Observe all federal, state, and local regulations. Precautions to be Taken in Handling and Storing Avoid skin contact. Avoid heat, acid or acid fumes. Keep in a cool, dry place. Other Precautions Do not ingest more than the one taste strip provided by your instructor. Section VIII - Control Measures Respiratory Protection (Specify Type) None needed under normal conditions with adequate ventilation. Ventilation Local Exhaust Yes Special None Mechanical (General) Yes Other None Protective Gloves Eye Protection Yes Splash-proof goggles Other Protective Clothing or Equipment Impervious clothing to prevent skin contact Work/Hygienic Practices