Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Student Exploration Sheet: Growing Plants
Document related concepts
Transcript
Name: ______________________________________ Date: ________________________ Student Exploration: Mouse Genetics (One Trait) Prior Knowledge Questions (Do these BEFORE using the Gizmo.) The image shows a single litter of kittens. How are they similar to one another? _______________ ___________________________________________________ How do they differ from one another? _______________ _____________________________________________________ What do you think their parents looked like? _________________________________________ ____________________________________________________________________________________ Gizmo Warm-up Heredity is the passage of genetic information from parents to offspring. The rules of inheritance were discovered in the 19th century by Gregor Mendel. With the Mouse Genetics (One Trait) Gizmo™, you will study how one trait, or feature, is inherited. Drag two black mice into the Parent 1 and Parent 2 boxes. Click Breed several times. What do the offspring look like? _________________________________________________ The appearance of each mouse is also called its phenotype. Click Clear, and drag two white mice into the parent boxes. Click Breed several times. What is the phenotype of the offspring now? __________________________________________ Do you think mouse offspring will always look like their parents? ______________________ Explain: __________________________________________________________________ Activity A: Get the Gizmo ready: Click Clear. Patterns of Drag a black mouse and a white mouse into the inheritance parent boxes, but don’t click Breed yet. Question: What patterns are shown by offspring traits? Predict: What do you think the offspring of a black mouse and a white mouse will look like? ________________________________________________________________________ Observe: Click Breed several times. What do you see? _____________________________ Observe: Drag two offspring into the Holding Cages. These mice are called hybrids because their parents had different traits. Click Clear, and then breed the two hybrids. What do you see now? ______________________________________________________ Experiment: Turn on Show statistics. Click Breed until there are 100 offspring. How many offspring were black? ________ How many were white? ________ Explore: Try other combinations of mouse parents. Write the results of each experiment in your notes. When you have finished, answer the following questions. (Note: You can refer to the parents as “pure black,” “pure white,” or “hybrid.”) Which parent combination(s) yield only white offspring? ________________________________________ Which parent combination(s) yield only black offspring? _______________________________________ Which parent combination(s) yield a mixture of black and white offspring? _____________________ Challenge: Based on experiments similar to these, Gregor Mendel devised a theory of inheritance. Use your own observations to come up with your own explanation of how a trait such as fur color is passed down from parents to offspring. Write your explanation down below. If possible, discuss your theory with your classmates and teacher. Activity B: Genetics basics Get the Gizmo ready: Click Clear. Drag a black mouse and a white mouse into the parent boxes. Introduction: Inherited traits are encoded on a molecule called DNA (deoxyribonucleic acid). Genes are segments of DNA that control a particular trait. Most genes have several different versions, or alleles. The genotype is the allele combination an organism has. Question: How do alleles determine fur color? Observe: Turn on Show genotype. Move your cursor over a mouse to see its genotype. What is the genotype of the black parent? _______ White parent? _______ These mice are homozygous for fur color, meaning both alleles are the same. Click Breed. What is the genotype of the offspring mice? ___________ These mice are heterozygous for fur color, meaning the alleles are different. Analyze: Dominant alleles are always expressed when present. Recessive alleles are not expressed when the dominant allele is also present. Look at the two alleles for fur color. Which allele is dominant, and which fur color does it produce? _________________ Which allele is recessive, and which fur color does it produce? _________________ Predict: Place two of the Ff offspring into the Holding Cages. Click Clear, and then place them into the parent boxes. Which allele(s) could the offspring inherit from parent 1? ______________________ Which allele(s) could the offspring inherit from parent 2? ______________________ What are the possible genotypes of the offspring? ___________________________ ___________________________________________________________________ Experiment: Click Breed several times, and look at the genotypes of the offspring. Did you find all the predicted genotypes? Explain below. Activity C: Modeling inheritance Get the Gizmo ready: Click Clear. Drag a black mouse and a white mouse into the parent boxes. Question: How do scientists predict the genotypes of offspring? Model: Scientists use a Punnett square to model the different possible offspring genotypes from a parent pair. The parent genotypes are written across the top and side of the square, as shown. The four possible offspring genotypes are then filled in. The first square is filled in for you. Fill in the remaining squares. What are the genotypes of the offspring? __________________________________ What percentage of the offspring will have black fur? _________________________ What percentage of the offspring will have white fur? _________________________ Experiment: Click Breed several times. Were your predictions correct? ________________ Model: Use the Punnett squares below to model each parent combination. After filling in each Punnett square, predict the percentages of black and white offspring. Parent 1: Heterozygous black (Ff) Parent 2: Heterozygous black (Ff) Parent 1: Heterozygous black (Ff) Parent 2: Homozygous white (ff) Predicted % black offspring: ______ Predicted % black offspring: ______ Predicted % white Predicted % white offspring: ______ offspring: ______ Experiment: Turn on Show statistics and Show as approximate percentage. For each combination, breed approximately 500 offspring. Record the results in the table below. (Hint: To obtain an Ff mouse, breed an FF mouse to an ff mouse. Place two Ff offspring into the holding cages, click Clear, and then drag the Ff mice into the parent boxes.) Parent 1 Genotype Ff Parent 2 Genotype Ff Ff ff % Black offspring % White offspring Draw conclusions: How well did the Punnett squares predict the offspring percentages for each parent pair? ___________________________________________________________ _________________________________________________________________________ Summarize: In your own words, describe what heredity is and how it works in mice. Think and discuss: Do you think most traits are inherited the way mouse fur color is? _____ Why do you think this is? Student Exploration: Mouse Genetics (Two Traits) Prior Knowledge Questions (Do these BEFORE using the Gizmo.) A single coin is flipped four times. What do you think is the most likely outcome? Four heads Three heads, one tail Two heads, two tails One head, three tails Four tails All are equally likely What do you think are the odds of getting four tails in a row? Explain your answer. Gizmo Warm-up On the Mouse Genetics (Two Traits) Gizmo, drag mice into the Parent 1 and Parent 2 spaces, and then click Breed to see their offspring. Experiment with different combinations of parent mice. What must be true to have offspring with black fur? ________________________________ What must be true to have offspring with white fur? ________________________________ What must be true to have offspring with black eyes? ______________________________ What must be true to have offspring with red eyes? ________________________________ What must be true to have offspring with red eyes and white fur? ___________________ __________________________________________________________________________________ Activity A: Exploring inheritance Get the Gizmo ready: Click Clear. Turn on Show genotype. Question: What patterns appear when two traits are inherited? Observe: Breed a black-fur, black-eye mouse with a white-fur, red-eye mouse. Click Breed several times, and then drag two of the offspring into the Holding Cages below. Move the cursor over a mouse to see its genotype, or allele combination. What is the genotype of the black-fur parent? _______________________________ What is the genotype of the white-fur parent? _______________________________ What are the genotypes of the offspring? __________________________________ Analyze: The probability of an event is the likelihood that it will happen. Probability can be expressed as a percentage, such as 75%, as a decimal (0.75), or as a fraction (3/4). What is the probability that an offspring mouse will have black fur and black eyes? _______ Predict: Click Clear, and move the two mice from the Holding Cages into the parent box. What do you expect the offspring of these mice to look like? ___________________________________ Experiment: Click Breed, and record the genotypes of the offspring on a sheet of paper. Repeat this several times to see a variety of offspring. What genotypes do you see? _________________________________________________________________________ _________________________________________________________________________ Extend: Turn on Show statistics, and click Breed until there are 100 offspring. How many offspring have black fur and black eyes? __________________________ How many offspring have black fur and red eyes? ___________________________ How many offspring have white fur and black eyes? __________________________ How many offspring have white fur and red eyes? ___________________________ Activity B: Probability and genetics Get the Gizmo ready: Click Clear. Use the Gizmo to create an Ff Ee parent and an Ff ee parent. Introduction: If two events are independent, the probability of both events occurring together is equal to the product of their independent probabilities. For example, if there is a 1/2 chance of getting “heads” on a coin flip, there is a 1/2 • 1/2 = 1/4 chance of getting two heads in a row. Question: When traits are inherited, what is the probability of each offspring’s genotype? Model: To determine the probability of a trait combination such as black fur and red eyes, consider each trait separately. Fill in the Punnett square for each trait. Then determine the probability of black fur and the probability of red eyes. Express each probability as a fraction. Parent 1 fur genotype: Ff Parent 2 fur genotype: Ff Parent 1 eye genotype: Ee Parent 2 eye genotype: ee Probability of black fur: —— Probability of red eyes: —— Predict: Now multiply the probabilities together to find the probability of black fur and red eyes. Express your answer as a fraction and as a percentage: —— _____% Experiment: Turn on Show statistics. Check that the parent mice genotypes are Ff Ee and Ff ee. Click Breed until there are 500 offspring. How many of the offspring had black fur and red eyes? _______ What percentage of offspring had black fur and red eyes? _______ On your own: Use this method to find the probabilities of other offspring trait combinations, such as black fur/black eyes, white fur/black eyes, and white fur/red eyes. Compare each predicted percentage to the actual percentage. In general, did this method work well? Activity C: Expanded Punnett square Get the Gizmo ready: Click Clear. Use the Gizmo to create two Ff Ee parents. Introduction: A second method for calculating the probability of each offspring’s genotype is to use an expanded Punnett square. Question: How can a 4x4 square model the inheritance of two traits? Model: Each parent mouse will contribute one allele for fur color and another for eye color. If a parent mouse is Ff Ee, there are four possible allele combinations the parent could pass to its offspring: FE, Fe, fE, and fe. The combinations are written along the top and sides of the expanded Punnett square, as shown below. Fill in the empty spaces to complete the square. Then write the probability of each offspring’s phenotype (physical appearance) in the spaces to the right. Express each probability as a fraction and as a percentage. Black fur, black eyes: —— _____% Black fur, red eyes: —— _____% White fur, black eyes: —— _____% White fur, red eyes: —— _____% Experiment: Check that Show statistics is turned on. Be sure there are two Ff Ee parents. Click Breed until there are 500 offspring. Write the results in the table below. Trait combination: Number: Percentage: Black fur, black eyes Black fur, red eyes White fur, black eyes White fur, red eyes Analyze: How well did the results match the predictions of the Punnett square? On your own: Try other parent combinations. Use any method to predict the percentages of each offspring’s phenotype. Use the Gizmo to test your predictions.
