BIO 111: Mendelian Genetic Inheritance Paper.
BIO 111: Mendelian Genetic Inheritance Paper.
BIOLOGY Mendelian Genetics Investigation Manual MENDELIAN GENETICS Table of Contents 2 Overview 2 Outcomes 2 Time Requirements 2 Key 3 Background 7 Materials 8 Safety 8 Preparation 9 Activity 1 11 Disposal and Cleanup 12 Observations Overview An investigation of the inheritance of two characteristics, stem color and leaf plant height, will be conducted in this lab exercise using Wisconsin Fast Plants®. The inheritance of traits will be studied in three generations and the phenotypes will be recorded during the seedling stage. The seeds of one parent population and seeds for the F1 and F2 generations will be provided, so that predictions can be formulated. After the seeds germinate, the results will be analyzed, and predictions will be compared. The activities can be completed in eight days at the specified conditions.
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Outcomes • Distinguish between phenotypes for stem color and plant height for three generations of Wisconsin Fast Plants®. • Infer genetic traits from observed phenotypes. • Propose and test models for inheritance of the phenotypes for the plant specimens provided. • Compare the predicted results with the data collected. Time Requirements Preparation …………………………………………………………… 15 minutes Day 1 …………………………………………………………………… 30 minutes Day 4 ………………………………………………………………….. 30 minutes Day 5 ………………………………………………………………….. 45 minutes Day 8 ………………………………………………………………….. 30 minutes Key Personal protective equipment (PPE) goggles gloves apron follow link to video photograph stopwatch results and required submit warning corrosion flammable toxic environment health hazard Made ADA compliant by NetCentric Technologies using the CommonLook® software 2 Carolina Distance Learning Background The modern understanding of genetic inheritance is based, in part, on the research of Gregor Mendel (1822–1884), an Austrian monk who performed carefully controlled studies of trait inheritance in pea plants. As Mendel worked with peas, he discovered patterns in the physical traits in different generations of offspring. An example is seedling color, such as yellow or green seeds, or seedling texture, such as wrinkled or smooth seeds. These traits were passed from generation to generation in predictable patterns. Based on his findings, Mendel developed two important laws: the law of segregation and the law of independent assortment. Mendel’s first law, the law of segregation, states that individuals possess two alleles for each trait. When organisms are crossed, the offspring receive one allele from each parent for a particular trait. Alleles are different forms of the same gene that code for slightly different expression patterns of a genetic trait. The two alleles may or may not be identical. When two different alleles are present, the trait that is expressed is dominant; the allele that is not expressed is recessive. In one of Mendel’s experiments, the tall parent plant was homozygous dominant, meaning that both of its alleles were for the “tall” trait. BIO 111: Mendelian Genetic Inheritance Paper.
The short parent plant was homozygous recessive, because it possessed two matching “short” alleles. All the offspring in the first generation were heterozygous and had one “tall” allele and one “short” allele (e.g., tall/short). The heterozygous genotype resulted in expression of the dominant trait, which was the tall phenotype. At the time Mendel was working, there was no concept of a mechanism for inheritance. Terms such as phenotype, the physical expression of a trait, and allele, the genetic traits, which combine to create an individual’s genotype, did not exist. The use of these terms throughout this manual is a result of the “Modern Evolutionary Synthesis,” which combined the 19th century work of Charles Darwin and Gregor Mendel with 20th century theories of the molecular mechanisms of inheritance. Mendel’s second law, the law of independent assortment, says that all traits are inherited independently of one another. This means that wrinkled seeds will not always be yellow, and smooth seeds will not always be green. Instead, seeds can be yellow and wrinkled, green and wrinkled, yellow and smooth, or green and smooth. Mendel’s laws help explain heredity (which traits are passed from one generation to the next) and variation (the differences between parents and their offspring). BIO 111: Mendelian Genetic Inheritance Paper.
The genetic information for a specific trait is usually written with the same letter of the alphabet representing both alleles. An uppercase (capital) letter represents the dominant allele, and a lowercase letter denotes the recessive allele. The two alleles written together represent the genotype of an organism. For example, the genotype of a tall, homozygous-dominant parent can be written as TT, whereas the genotype of a short, homozygous-recessive parent can be written Tt. The genotype of the first generation continued on next page www.carolina.com/distancelearning 3 MENDELIAN GENETICS Background continued of offspring includes one allele from each parent and is denoted as Tt. The outward expression of genotype is the phenotype. This is what we see when we examine an organism. For example, the tall, first-generation pea plants in Mendel’s experiment exhibited the tall phenotype and the Tt genotype. Figure 1. The first two organisms that are crossed are called the Parental generation (P generation). All descendants of the P generation are part of the Filial generation (F generation). Offspring of the P generation are F1. The F1 offspring can be bred to each other, which in turn produce F2, which then produce F3, etc. When only one set of traits is being tracked in a cross, it is a monohybrid cross (i.e., if we are only interested in flower color). A cross that involves two sets of alleles is a dihybrid cross (i.e., tracking flower color and seed texture). A table called a Punnett square can be used to show the results of genetic crosses. BIO 111: Mendelian Genetic Inheritance Paper.
This useful tool was named for Reginald Punnett (1875–1967), a Cambridge biologist who verified and expanded on Mendel’s work. To draw a Punnett square, write one set of parental alleles across the top of the grid, and write the other set of alleles vertically down the left-hand side of the grid. For a monohybrid cross, each parental allele is listed separately in a column or row. Each box in the Punnett square represents a specific combination of parental alleles and is determined by column and row placement. Fill in each box by writing the allele for the column and the allele for the row side-by-side. Refer to Figure 1, which shows how to draw a Punnett square for a monohybrid cross. Before conducting studies on inheritance, biologists typically establish true-breeding (homozygous) stocks for the traits they are interested in studying. For most controlled genetic studies, the individuals in the P generation (P1 and P2) will be homozygous for the traits in question. Punnett squares can also be used to calculate the probability of an offspring having a given genotype, or to calculate the expected distribution of genotypes in the F1 and F2 generations. For instance, in the continued on next page 4 Carolina Distance Learning cross demonstrated in Figure 1, one parent is homozygous dominant for the gene in question (AA) and the other is homozygous recessive for the same gene (aa). Completing the cross in the Punnett square shows that all possible combinations of alleles will result in a heterozygous individual. There is a 100% probability that any individual in the F1 generation will have the genotype Aa. Said another way, we would expect 100% of the offspring to have the genotype of Aa. If the F1 generation are crossed back to each other the cross would be expressed as seen in Figure 2. To calculate the probability that an individual offspring will have a particular genotype, add the number of times that genotype appears in the table and divide by the total number of possibilities (Table 1). In this case, Aa appears twice; so, two divided by four is 0.5, giving us a 1:2 probability that any given offspring will be Aa. We would also expect that 50% of the offspring in that generation will have that genotype.
Similarly, AA and aa only appear once. One divided by four is 0.25, so 25% of the offspring will have either of those genotypes; see Table 1. Since the combination of genes during mating is a mostly random occurrence, actual percentages may vary in real populations, but the larger the population is, the closer to these ratios the data will be. Table 1. Genotype Percentage AA ¼ = 0.25 = 25% Aa 2 aa ¼ = 0.25 = 25% ¼ = 0.5 = 50% Probabilities for multiple genes can be calculated by multiplying the probabilities of each genotype together. If pea plants homozygous for the tall gene (TT) and homozygous for the yellow pea gene (YY) were crossed with plants heterozygous for both traits (TtYy) (Figure 3), the crosses would each result in 50% homozygous dominant and 50% heterozygotes (Table 2). To determine the expected percentage of TTYY individuals in the F1 generation, the odds of TT (0.5) are multiplied by the odds of YY (0.5) yielding a probability of 0.25 or 25% (Table 3). Figure 3. Figure 2. continued on next page www.carolina.com/distancelearning 5 MENDELIAN GENETICS Background continued Table 2.
Genotype TT Percentage ¼ = 0.5 = 50% 2 Tt 50% tt 0% YY 50% Yy 50% yy 0% Table 3. 6 Genotype Percentage TTYY 0.5 × 0.5 = 0.25 = 25% TtYY 0.5 × 0.5 = 0.25 = 25% ttYY 0 × 0.5 = 0 = 0% TTYy 0.5 × 0.5 = 0.25 = 25% TtYy 0.5 × 0.5 = 0.25 = 25% ttYy 0 × 0.5 = 0 = 0% TTyy 0.5 × 0 = 0 = 0% Ttyy 0.5 × 0 = 0 = 0% ttyy 0 × 0.5 = 0 = 0% Carolina Distance Learning Materials Needed from the equipment kit: Included in the materials kit: Fast Plants® seed types (1 envelope with 15 P1 seeds) 6 Petri dishes Fast Plants® seed types (1 envelope with 15 F1 seeds) 10 Filter papers Fast Plants® seed types (1 envelope with 50 F2 seeds) Graduated pipet Reorder Information: A replacement investigational kit for Mendelian Genetics (item number 580108) can be ordered from Carolina Biological Supply Company. Call: 800.334.5551 to order. Metric ruler Forceps Beaker Needed but not supplied: • Tap water, 200 mL • Fluorescent light source • Pencil • Scissors Note: Fast Plants® seeds are genetically engineered to grow extremely fast and are very sensitive to heat. If a common incandescent light source is used, the heat from the light will “cook” the seeds, and they will not grow. A cool light source needs to be used for this experiment. A fluorescent light or LED is needed to provide a cool, white light source. Inexpensive fluorescent light bulbs are now readily available and will fit into a traditional desk lamp. www.carolina.com/distancelearning 7 MENDELIAN GENETICS Safety Read all of the instructions for this laboratory activity before beginning.
Follow the instructions closely. Remember to observe established laboratory safety practices, including the use of appropriate personal protective equipment. Do not eat, drink, or chew gum while performing this activity. Wash your hands with soap and water before and after performing the activity. Clean up the work area with soap and water after completing the investigation. Keep pets and children away from lab materials and equipment. 8 Carolina Distance Learning Preparation 1. Read through the procedure. 2. Clean and sanitize the work space. 3. Prepare a fluorescent light area. This area should contain a fluorescent light that can be raised and lowered, so that it maintains a height of 5–10 cm above the Fast Plants®. Fast Plants® seeds are very small. Forceps may be helpful for positioning the seeds in the Petri dishes. If your envelope does not contain the stated number of seeds, do not worry.
The percentage of seeds will be used for all of the calculations. ACTIVITY ACTIVITY 1 A Day 1 In this activity, plants from one of the truebreeding parent populations and from the first generation of offspring will be grown up. Based on the results, predictions will be made about the genotypes for these populations, and the phenotype and genotype of both the other parent population and the F2 generation. Planting P1 and F1 Generations 1. Cut a sheet of filter paper into four strips of approximately 1 cm × 8 cm each. Set the remaining filter paper aside. 2. Place approximately 3 cm of the end of a filter paper strip into the inverted lid (larger half) of a Petri dish. 11. Carefully place both dishes under a fluorescent light source. (The light should be 5–10 cm above the Petri dish.) 12. Place another Petri dish under the lamp, and fill the bottom (smaller half) with water. 13. Place the protruding ends of the P1 and F1 filter paper strips into the dish of water. See Figure 4. 14. Place the lid (larger half) on the water dish. Check this dish daily to make sure it does not dry out during the course of the experiment. Figure 4. 3.
Use a pipet to place two or three drops of water on the end of the filter paper strip in the Petri dish. This will help to hold the filter paper in the dish. 4. Use a pencil to label one of the whole pieces of filter paper “P1.” The filter paper strip will act as a wick to keep the Fast Plant® seed moist. Therefore, place as much of the filter paper strip as possible into the water dish. Minimize the amount of filter paper exposed to the air; the goal is to prevent the paper from drying out. 5. Place the labeled piece of filter paper in the Petri dish that contains the filter paper strip. 6. Pour water into the Petri dish, and saturate the filter paper thoroughly. 7. Pour off the excess water. 8. Evenly space 10 of the P1 seeds around the labeled filter paper. 9. Place the bottom (smaller half) of the Petri dish above the inverted lid to form a dome. The filter paper strip should extend out from the closed Petri dish. 10. In a new petri dish, repeat Steps 2–9 with the F1 seeds, but label the filter paper “F1.” B Day 4 Scoring On Day 4, examine the seedlings for the purple stem trait and the dwarf stem height trait. Purple pigment in any part of the leaves or stem indicates that the purple stem trait is present. Stems that are shorter than a plant with a normal stem continued on next page www.carolina.com/distancelearning 9 ACTIVITY ACTIVITY 1 continued height are said to have the dwarf stem height trait (See Figure 5 for comparison). Figure 5. C Day 5 Planting F2 Generation 1.
Fill the bottom of a Petri dish with water. This will be the water reservoir for all five Petri dishes in this investigation. 2. Cut five strips of filter paper to approximately 1 cm × 8 cm each. Set the remaining filter paper aside. 3. Place approximately 3 cm of the end of a filter paper strip into the inverted lid (larger half) of one Petri dish. 4. Use a pencil to label an uncut piece of filter paper “F2.” 5. Place the labeled piece of filter paper in the Petri dish that contains the filter paper strip. 1. Count the number of plants that have: • A purple stem and a dwarf stem height • A purple stem and a normal stem height • A non-purple stem (green stem) and a dwarf stem height • A non-purple stem (green stem) and a normal stem height 2. Record the results in Data Table 1. 3. Determine the percentage of each generation that has each phenotype. 4. Record these percentages in Data Table 1. 5. Rinse the Petri dishes with water, and dry them with paper towels. Prediction Based on your observations of the P1 and F1 generations, what would you expect the P2 to look like if you had grown it? Predict the phenotypes that are likely to be observed in the F2 generation, and predict the corresponding proportions of each phenotype. Record this in Data Table 2.
10 Carolina Distance Learning 6. Pour water into the Petri dish and saturate the filter paper thoroughly. 7. Pour off the excess water. 8. Evenly space 10 of the F2 seeds around the labeled filter paper. 9. Place the bottom half of the Petri dish on top of the inverted lid to form a dome. The filter paper strip should extend out from the closed Petri dish. 10. Place one end of the filter paper strip (from Step 3) into the reservoir Petri dish and the other end into the Petri dish that contains the seeds. 11. Repeat Steps 3–10 to set up 4 more identical plates, each with 10 seeds.
Each Petri dish that contains seeds will be connected to the water reservoir with a filter paper strip. 12. Place the lid on the water reservoir Petri dish. Check this dish daily to ensure that the water does not dry out. 13. Carefully place the fluorescent light source above all 6 Petri dishes. Disposal and Cleanup 1. Dispose of the Fast Plants® in the trash. 2. Wash the Petri dishes with soap and water and return them to your kit. 3. Sanitize the work space. Note: Make sure the light is 5–10 cm from the top of the Petri dish. D Day 8 Scoring Repeat the scoring procedure that you used on Day 4 for the F2 seeds to determine expression of the purple stem trait and the dwarf stem height trait.
Record the results and percentages in Data Table 2. Use the forceps to carefully remove the seed plants and place on a paper towel. Organize these into the four categories shown in Data Table 2 and take a photograph of this setup. www.carolina.com/distancelearning 11 ACTIVITY Observations Data Table 1. Genetic Inheritance Number of Plants with: P1 Generation Purple stem and dwarf stem height Purple stem and normal stem height Non-purple stem and dwarf stem height Non-purple stem and normal stem height Total number of plants 12 Carolina Distance Learning P1 Generation Percentage F1 Generation F1 Generation Percentage Data Table 2. F2 Genetic Inheritance Number of Plants with: F2 Generation Prediction F2 Generation Percentage Prediction F2 Generation Actual F2 Generation Percentage Actual Purple stem and dwarf stem height Purple stem and normal stem heigh Non-purple stem and dwarf stem height Non-purple stem and normal stem height Total number of plants www.carolina.com/distancelearning 13 BIOLOGY Mendelian Genetics Investigation Manual www.carolina.com/distancelearning 866.332.4478 Carolina Biological Supply Company www.carolina.com • 800.334.5551 ©2020 Carolina Biological Supply Company CB780312003 V2.2 Mendelian Genetic Inheritance Student Name Date Instructions: 1. Please read all of the introduction and background information within the investigative manual. a. Once you have done so answer the prelab question BEFORE completing any of the lab’s activities. 2. Once you have completed the prelab questions proceed to the activities of the lab within the investigative manual. a. As you read through the instructions for completing each activity make sure you also: i. Complete any instructions (append photos, etc)/ and answer any questions found in the post lab questions for each activity. ii. Take the photos of your experiments in each activity as directed below. IMPORTANT: Don’t clean-up your lab until you know what portion of the experiment you need to take a picture of. 3. Here is a video that will introduce you to the lab and its main concepts. The student is encouraged to watch it. a. Mendelian Genetics Prelab Questions 1.
As described in the investigative manual Gregor Mendel made careful observations of pea plants and the traits of their offspring in order to develop the law of segregation and independent assortment. Pea plants that are tall are expressing the dominant “tall” gene (T). Plants that had yellow pigmentation are expressing the dominant “yellow” gene (Y). In the space below complete a Punnett square of a cross between P1 and P2 where P1 is homozygous dominant in both traits and P2 is homozygous recessive in both traits. 2. What are the possible genotypes and phenotypes of the offspring in the F1 generation? Express your answer as a percent for each genotype and each phenotype. 1 © 2016 Carolina Biological Supply Company 3. Having now completed the P1/P2 cross let’s proceed to cross members of the F1 generation. In the space below produce a Punnett square that crosses a male and female from the F1 generation to produce the F2 generation. If you need help setting up this Punnett square check out this website. 4. What are the possible genotypes and phenotypes of the offspring in the F2 generation? Express your answer as a percent for each genotype and each phenotype seen in the Punnett square. 5.
In consideration of what you have done this far let’s reflect on the laws of genetic inheritance and the recent discoveries made regarding cellular division. In our last lab we studied both mitosis and meiosis. In meiosis we saw how a cell could divide to make four gametes (sperm or egg). The process of meiosis had not been discovered when Gregor Mendel proposed the law of segregation and law of independent assortment. How do the findings of the process of meiosis confirm what Mendel had proposed in his laws of genetic inheritance? 6. Now proceed to read the investigative manual. Notice that the experiment takes 8 total days, and you collect data on day 4 and day 8. Read through all of day 4’s instruction and fill out your purpose and hypothesis statement (found beneath table 1 below) before proceeding to day 5 and the 2nd half of the lab. Keep in mind that your hypothesis is something that needs to testable. In other words, you need to be able to support it or refute it with the data you collect in the 2nd half of the lab.
7. Hint for table 1 data: Keep in mind that in these types of experiments, as stated in the investigative manual, the parental generations are typically homozygous. 2 © 2016 Carolina Biological Supply Company Activity 1 Instructions: 1. Open the investigative manual. Locate all the needed materials supplied in the kit and those you will need to supply yourself. 2. Lay them out in your work area. 3. Read through the entire set of instructions found in the investigative manual for the activity to avoid making mistakes when you go to execute the experiment. 4. Once you have read through the instructions go back to step 1 and begin executing the experiment. 5. Please answer the questions below and/or append appropriate representations of data (photos, graphs, etc). REMEMBER don’t clean up until you have taken the appropriate photos of your experiment as described below. Data Table 1: Genetic Inheritance Number of Plants with: P1 Generation P1 Generation Percentage F1 Generation Purple stem and dwarf stem height Purple stem and normal stem height Non-purple stem and dwarf stem height Non-purple stem and normal stem height Total number of plants 3 © 2016 Carolina Biological Supply Company F1 Generation Percentage Purpose statement: (This should be the question the experiment is attempting to address.
It should be written as a question.) Hypothesis statement: (This should be an “if/then” testable prediction that addresses the question/purpose of the lab.) Evidence/Claim statement: (This should be a statement regarding whether your hypothesis was supported or refuted and what data/evidence allows you to make this claim.) Reflection statement: (This should be a statement of what you learned, how your understanding changed, if you have new questions, and what connections can you make between the lab and the content in the book and other assignments.) Photo 1 – Activity 1 Take a picture and insert the image(s) of one of your F2 generation petri dishes from the scoring set of the “Day 8” section in activity 1 of the investigative manual: 4 © 2016 Carolina Biological Supply Company Data Table 2: F2 Genetic Inheritance Number of Plants with: F2 Generation Prediction F2 Generation Percentage Prediction F2 Generation Actual F2 Generation Percentage Actual Purple stem and dwarf stem height Purple stem and normal stem height Non-purple stem and dwarf stem height Non-purple stem and normal stem height Total number of plants 1. Having now collected your data for the F2 generation go back and fill out your evidence/claim statement and also your reflection statement. After doing so answer the questions below.
2. Is the Purple Stem trait dominant or recessive? Support your conclusion with examples from your laboratory observations. 5 © 2016 Carolina Biological Supply Company 3. Is the dwarf stem height trait dominant or recessive? Support your conclusion with examples from your laboratory observations. 4. Based on your observations, what are the phenotype and genotype of the P1 plant? What did you deduce to be the genotype and phenotype of the P2? Use P/p designations for stem color and H/h designations for stem height. 5. Based on your observations, draw the Punnett square for the cross of the P1 and P2 parental plants. Use P/p designations for stem color and H/h designations for stem height as above. 6 © 2016 Carolina Biological Supply Company 6. BIO 111: Mendelian Genetic Inheritance Paper.
Based on your observations, draw the Punnett square for the cross of the F1 plants. a. Based on the Punnett square above, what is the percentage of offspring that are predicted to have purple stems and dwarf stem height? How did this compare to the results that you obtained in this lab? b. Based on the Punnett square above, what is the percentage of offspring that are predicted to have non-purple stems and dwarf stem height? How did this compare to the results that you obtained in this lab? 7 © 2016 Carolina Biological Supply Company c. Based on the Punnett square above, what is the percentage of offspring that are predicted to have purple stems and normal stem height? How did this compare to the results that you obtained in this lab? d. Based on the Punnett square above, what is the percentage of offspring that are predicted to have non-purple stems and normal stem height? How did this compare to the
BIO 111: Mendelian Genetic Inheritance Paper.
BIO 111: Mendelian Genetic Inheritance Paper.
BIO 111: Mendelian Genetic Inheritance Paper.