HEREDITARY STUDENT PACKET # 5 Name: Date: Big Idea 16: Heredity and Reproduction Benchmark: SC.7.L.16.1: Understand and explain that every organism requires a set of instructions that specifies its traits, that this hereditary information (DNA) contains genes located in the chromosomes of each cell, and that heredity is the passage of these instructions from one generation to another. (Also Assesses SC.7.L.16.2, SC.7.L.16.3) Vocabulary: allele, DNA, dominant allele, gene, genotype, heterozygous, homozygous, hybrid, inheritance, phenotype, Punnett square, recessive allele, trait Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 1. The image shows a single litter of kittens. How are they similar to one another? 2. How do they differ from one another? 3. What do you think their parents looked like? Gizmo Warm-up The rules of inheritance were discovered in the 19 th century by Gregor Mendel. With the Mouse Genetics (One Trait) Gizmo, you will study how one trait, or feature, is inherited. 1. Watch as I drag two black mice into the Parent 1 and Parent 2 boxes. I will click Breed several times. What do the offspring look like? The appearance of each mouse is also called its phenotype. 2. Now, I ll drag two white mice into the parent boxes. I ll Breed them several times. What is the phenotype of the offspring now? 3. Do you think mouse offspring will always look like their parents? Explain: 2011-2012 Science Saturday Enrichment Tutorial Page 1
Activity A: Patterns of inheritance To Get the Gizmo ready: I will Drag a black mouse and a white mouse into the parent boxes. Question: What patterns are shown by offspring traits? 1. Predict: What do you think the offspring of a black mouse and a white mouse will look like? 2. Observe as I Breed them several times. What do you see? 3. Observe as I Drag two offspring into the Holding Cages. These mice are called hybrids because their parents had different traits. I ll breed the two hybrids. What do you see now? 4. Experiment: We ll take a look at some statistics. I ll breed the mice until there are 100 offspring. How many offspring were black? How many were white? 5. Explore: We ll try some other combinations of mouse parents. Write the results of each experiment in your notes. After we have finished experimenting, answer the following questions. (Note: You can refer to the parents as pure black, pure white, or hybrid. ) a. Which parent combination(s) yield only white offspring? b. Which parent combination(s) yield only black offspring? c. Which parent combination(s) yield a mixture of black and white offspring? 6. 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 on an extra sheet of paper and attach it to this worksheet. If possible, discuss your theory with your classmates and teacher. Activity B: Genetics basics To Get the Gizmo ready, I will Drag a black mouse and a white mouse into the parent boxes. 2011-2012 Science Saturday Enrichment Tutorial Page 2
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? 1. Observe: I will move the cursor over a mouse to see its genotype. a. What is the genotype of the black parent? White parent? These mice are homozygous for fur color, meaning both alleles are the same. b. What is the genotype of the offspring mice? These mice are heterozygous for fur color, meaning the alleles are different. 2. 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. a. Which allele is dominant, and which fur color does it produce? a. Which allele is recessive, and which fur color does it produce? 3. Predict: I will place two of the Ff offspring into the Holding Cages. After clearing the Gizmo, I will place them into the parent boxes. A. Which allele(s) could the offspring inherit from parent 1? B. Which allele(s) could the offspring inherit from parent 2? C. What are the possible genotypes of the offspring? 4. Experiment: I will click Breed several times, and you should observe the genotypes of the offspring. Did you find all the predicted genotypes? Explain. Activity C: Modeling inheritance Get the Gizmo ready: I will Drag a black mouse and a white mouse into the parent boxes. Question: How do scientists predict the genotypes of offspring? 2011-2012 Science Saturday Enrichment Tutorial Page 3
1. 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. a. What are the genotypes of the offspring? b. What percentage of the offspring will have black fur? c. What percentage of the offspring will have white fur? 2. Experiment: I will click Breed several times. Observe the offspring. Were your predictions correct? 3. 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) Predicted % black offspring: Predicted % white offspring: Parent 1: Heterozygous black (Ff) Parent 2: Homozygous white (ff) Predicted % black offspring: 2011-2012 Science Saturday Enrichment Tutorial Page 4
Predicted % white offspring: 4. Experiment: We will examine some statistics which show the results as an approximate percentage. For each combination, I will breed approximately 500 offspring. Record the results in the table below. (Hint: To obtain an Ff mouse, I will breed an FF mouse to an ff mouse. I will place two Ff offspring into the holding cages, while I prepare the Gizmo. Then, I will drag the Ff mice into the parent boxes.) Parent 1 Genotype Parent 2 Genotype % Black offspring % White offspring Ff Ff Ff ff 5. Draw conclusions: How well did the Punnett squares predict the offspring percentages for each parent pair? 6. Summarize: In your own words, explain how traits are passed from parents to their offspring. 7. Think and discuss: Do you think most traits are inherited the way mouse fur color is? Why do you think this is? 8 If a new breed of black fur (BB) mouse and a new breed of white fur (WW) mouse mated, and all the offspring were gray fur (BW), what would this indicate? 2011-2012 Science Saturday Enrichment Tutorial Page 5
EXTENSION Paper Pet Breeding Student Name Get ready to breed your pet with a classmate s pet of the opposite sex. Step 1: Determine the alleles (the genotype) for the pet you designed. The dominant alleles are: B blue skin R round eyes T triangular nose P pointed teeth For each of the dominant traits that your pet has, you may choose what the other allele will be. For example, for skin, your alleles may be BB or Bb. The alleles for the recessive traits must be homozygous. bb yellow skin rr square eyes tt oval nose pp square teeth Step 2: Write the appropriate alleles for each phenotype that your pet has on the back of your pet. Draw 2 rod-shaped chromosomes with the alleles from the female written on the first chromosome and the alleles (in the same order) from the male on the other. Step 3: Find a classmate with a pet of the opposite sex. Your pets will have four offspring. Prepare 4 data logs (one for each of the 4 offspring) like the one below. Offspring # Trait Skin color Eye shape Nose shape Tooth shape Sex Female Allele Male Allele Offspring s Genotype Offspring s Phenotype Step 4: For each trait, use coin tosses when necessary to determine which allele the offspring will inherit from each parent (Heads can represent the dominant trait, tails can represent the recessive.) If a parent is homozygous, there s no need to toss the coin! To determine the sex, it will not be necessary for the female to toss the coin because the only allele she can contribute is an X. For the male, heads can represent X and tails can represent Y. Remind students that the genotype XY will be male and XX, female. Step 5: Use the results in your data log to draw and color the paper pet for each offspring, showing the traits (the phenotypes) that each one has inherited. Write the genotype for each trait on their backs. Draw big ears and long whiskers on the face of each offspring that is a male and small ears with short whiskers on each female. 2011-2012 Science Saturday Enrichment Tutorial Page 6
Activity 2: A Monohybrid Cross for Fur Color Student Directions and Answer Sheet Student Name _ Objective: Model an offspring s inheritance of alleles from heterozygous parents with a simple experiment. Problem Statement: What proportion of offspring will inherit recessive, yellow fur if both parents are heterozygous for fur color? Background Information: (What should you do to predict the probable results?) Hypothesis: Procedure: Step 1: Choose another student who has a paper pet of the opposite sex from the one you created in the Engage Activity. Step 2: Put masking tape on each side of the coin. Label one side of your coin with B for blue fur. Label the other side of your coin with b for yellow fur. Step 3: One student from each male/female pet partnership should prepare a data log with 4 columns and rows. Label each column heading in the following order: Trial #, Allele from Female, Allele from Male, and last, Offspring s Allele. Each row in the first column should be numbered from 1-20, representing the 20 coin tosses that you will do. Step 4: To model reproduction, each student flips a coin. The student with the coin that represents the female pet parent records the allele that turns face up. The other student records the allele from the coin of the male pet parent. The offspring s genotype is recorded. Repeat this experiment 20 times and record the results. Step 5: When all the data has been collected, tally the results for each combination of alleles. Analyze results: How many of these combinations would be homozygous recessive? How many would be homozygous dominant? How many would be heterozygous? How many crosses would produce pets with blue fur? How many would have yellow fur? Convert the results to percentages. (Divide the number of blue pets by 20. Then, divide the number of yellow pets 20). _ Conclusion: What was the percentage of pets with yellow fur? How close were these results to the ratios predicted by Mendel s Laws which were calculated from the results in the Punnett square? Does the data support the hypothesis? 2011-2012 Science Saturday Enrichment Tutorial Page 7
ASSESSMENT NAME: _ DATE: Big Idea 16: Heredity and Reproduction Benchmark: SC.7.L.16.1: Understand and explain that every organism requires a set of instructions that specifies its traits, that this hereditary information (DNA) contains genes located in the chromosomes of each cell, and that heredity is the passage of these instructions from one generation to another. (Also Assesses SC.7.L.16.2, SC.7.L.16.3) Multiple Choice Identify the choice that best completes the statement or answers the question. 1 The diagram shows a Punnett square of the cross between the eye colors of two animals. Brown eye color is dominant and blue eye color is recessive. What is the percentage of offspring with brown eyes as shown by the data? A 0% B 25% C 50% D 100% 2 In pea plants, purple flower color is dominant to white flower color. Susan has pea plants in her garden. Most of them have purple flowers, while some have white flowers. If she crosses two pea plants that have white flowers, what color flowers will the resulting pea plants have? F 100% purple G 100% white H 50% purple and 50% white J 75% purple and 25% white 3 Which of these determines whether a fertilized egg develops into a toad, a snake, or a lizard? A the sex of the egg B the age of the egg C the size of the egg D the genes of the egg 2011-2012 Science Saturday Enrichment Tutorial Page 8
4 In guinea pigs, brown hair is dominant to white hair. The diagram shows chromosomes from a male guinea pig with brown hair and a female guinea pig with white hair. A white-haired offspring resulting from the cross of these two guinea pigs MOST likely inherited genes from which two chromosomes? F 1 and 2 G 1 and 3 H 2 and 4 J 3 and 4 5 Brown hair and brown eyes are dominant traits in humans. If both parents have brown hair and brown eyes, how is it possible that their children can have blond hair and blue eyes? A Both parents are homozygous for brown eyes. B Both parents are homozygous for blond hair. C The children inherited one recessive gene from each parent. D The children inherited one dominant gene from each parent. 6 The Punnett square shows the cross between cabbage butterflies. and Why are all the offspring white? F Both parent butterflies were dominant for white color. G Only one parent butterfly carried recessive yellow traits. H Only one parent carried dominant and recessive color genes. J Both parent butterflies carried recessive genes for yellow color. 2011-2012 Science Saturday Enrichment Tutorial Page 9
7 The allele for dimples is dominant and the allele for no dimples is recessive. If two parents that are heterozygous for dimples produce a child, what are the chances the child will have dimples? A 25% B 50% C 75% D 100% 8 A male fruit fly is homozygous dominant for gray body color (G) and is crossed with a female fruit fly that is homozygous recessive for ebony body color (g). What are the probable phenotypes of the offspring? F 25% gray, 75% ebony G 50% gray, 50% ebony H 100% ebony J 100% gray 9 In rabbits, brown fur color (F) is dominant to white fur color (f). If two rabbits with brown fur produce a baby with white fur, what are the genotypes of the parents? A FF and Ff B Ff and Ff C FF and FF D ff and ff 10 If a homozygous tall (T) pea plant is crossed with a homozygous short (t) pea plant, what will their offspring look like? F They will all be tall. G They will all be short H Half of them will be tall and half will be short. J Three quarters of them will be tall and one quarter will be short. 2011-2012 Science Saturday Enrichment Tutorial Page 10