Unit 8: GENETICS PACKET

Transcription

1 Unit 8: GENETICS PACKET This packet is designed to help you understand several concepts about GENETICS. As you practice the exercises on each handout, you will be able to: Make and defend a claim based on evidence that inheritable genetic variations may result from: combinations, replication & mutations. (HS-LS3-2) Use Punnett square to predict the results of genetic crosses: monohybrid & dihybrid (ratio & probability). (HS10-LS3-2.1) Determine genotype and phenotype of a parent organism: heterozygous, homozygous. (HS10-LS3-2.2) Determine genotype and phenotype of an offspring: heterozygous, homozygous. (HS10-LS3-2.3) Explain Mendel s Principles of Genetics: Law of Segregation and Law of Independent Assortment. (HS10-LS3-2.4) Record this packet in the Table of Contents for Unit 8. This will be the next HANDOUT. Contained in this Packet: 1. Genetic Probabilities & Monohybrid Crosses 2. Dihybrid Crosses: Crosses that Involve 2 Traits 3. Virtual Lab: Punnett Squares

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3 UNIT 8: GENETICS Genetic Probabilities & Monohybrid Crosses Reproduction is a necessary part of being alive. All living things have the ability to create offspring either sexually or asexually. Regardless of the method, reproduction is a way for genetic information contained in DNA to be passed from one generation to the next generation. This genetic information comes in the form of genes and alleles. These genes and alleles control the physical characteristics that will be expressed in the resulting offspring. Understanding how these genes/alleles are passed to the next generation AND how they will be expressed is the reason why scientists study genetics. Objectives: The purpose of this activity is to provide practice so that students can: Use Punnett square to predict the results of genetic crosses: monohybrid & dihybrid (ratio & probability). (HS10-LS3-2.1) Determine genotype and phenotype of a parent organism: heterozygous, homozygous. (HS10-LS3-2.2) Determine genotype and phenotype of an offspring: heterozygous, homozygous. (HS10-LS3-2.3) Directions: Using your notes and the textbook (pgs ), answer the following questions about genetic crosses involving 1 trait (monohybrid crosses) 1. Identify each as an example of a gene or an allele (don t abbreviate please). black hair blue eyes eye color height thin lips nose size 2. Identify each as either a genotype (geno) or a phenotype (pheno). curly hair unibrow EE attached ear lobes YyBb hairy knuckles skin tone fat nose DDaa Gg 3. Identify each genotype as heterozygous (He), homozygous dominant (HoD) or homozygous recessive (HoR). RR Bb dd Pp ff qq AA Gg ww BB 4. What is the point of setting up a Punnett Square? 5. Set up a Punnett Square showing the cross between a homozygous brown dog and a homozygous white dog with black spots. D = white with black spots d = brown a) What are all the possible genotypes for offspring as seen in question #5? b) Set up a ratio that includes all possible genotypes as seen in question #5. c) What are all the possible phenotypes as seen in question #5? d) Set up a ratio that includes all possible phenotypes as seen in question #5. e) When a homozygous dominant individual produces offspring with a homozygous recessive individual (like in question #5), all offspring from this cross in the first generation will be homozygous / heterozygous for all traits.

4 6. Set up a Punnett Square that shows a cross between two of the offspring of question #5. a) What are all the possible genotypes for offspring as seen in question #6? b) Set up a ratio that includes all possible genotypes as seen in question #6. c) Set up a ratio that includes all possible phenotypes as seen in question #6. 7. Some alleles are neither dominant nor recessive. Gender determining alleles are one example. Explain why the human male is responsible for determining the gender of his offspring? Set up a Punnett Square that supports your explanation. (genotype human male: XY, genotype human female: XX) Explanation Punnett Square 8. In watermelons, green skinned color is dominant (G) over striped skinned watermelons (g). Cross a heterozygous green watermelon with a striped skinned watermelon. a) Draw a Punnett Square that shows all possibilities of this cross. b) Give all possible ratios for each genotype and each phenotype. c) Calculate the probability (%) that each genotype and phenotype will occur. Genotype Ratios Phenotype Ratio Genotype Probability Phenotype Probability 9. In dogs, black coat color is dominant (E) over white coat color (e). Cross a heterozygous female with a heterozygous male. a) Draw a Punnett Square that shows all possibilities of this cross. b) Give all possible ratios for each genotype and each phenotype. c) Calculate the probability (%) that each genotype and phenotype will occur. Genotype Ratios Phenotype Ratio Genotype Probability Phenotype Probability

5 10. In horses, black coat color is dominant (B) over brown coat (b). When a black stallion (male) is crossed with a brown mare (female), the offspring were 50% black and 50% brown. a) What is the genotype of the stallion and the mare? b) Draw a Punnett Square as evidence. Genotype of Stallion (male) Genotype of Mare (female) Use the scenario below to answer questions # A pet store sells hamsters. Customers have their choice between brown hamsters or white hamsters. Customers prefer hamsters with brown fur to hamsters with white fur. With this in mind, the owner crossed a female with brown fur and a male with white fur hoping to get babies with brown fur. When the baby hamsters were born, 3 of the 10 offspring were born with brown fur. 11. Based on the information provided, which fur color could be considered dominant? 12. Based on the information provided, which fur color could be considered recessive? 13. Based on questions #11 & 12, what is the genotype of each parent (G = dominant; g = recessive)? Genotype Male Hamster Genotype Female Hamster 14. EXPLAIN how two brown hamsters could produce babies with white fur? 15. EXPLAIN how the pet store owner could breed a litter of only brown hamsters? (Set up a Punnett Square that supports your explanation.) Explanation Punnett Square

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7 UNIT 8: GENETICS Dihybrid Crosses: Genetic Crosses That Involve 2 Traits Reproduction is a necessary part of being alive. All living things have the ability to create offspring either sexually or asexually. Regardless of the method, reproduction is a way for genetic information contained in DNA to be passed from one generation to the next generation. This genetic information comes in the form of genes and alleles. These genes and alleles control the physical characteristics that will be expressed in the resulting offspring. Understanding how these genes/alleles are passed to the next generation AND how they will be expressed is the reason why scientists study genetics. Objectives: The purpose of this activity is to provide practice so that students can: Use Punnett square to predict the results of genetic crosses: monohybrid & dihybrid (ratio & probability). (HS10-LS3-2.1) Determine genotype and phenotype of a parent organism: heterozygous, homozygous. (HS10-LS3-2.2) Determine genotype and phenotype of an offspring: heterozygous, homozygous. (HS10-LS3-2.3) Directions: Using your notes and the textbook (pgs ), answer the following questions about genetic crosses involving 2 traits (dihybrid crosses) In rabbits, grey hair is dominant (G) to white hair (g) and black eyes are dominant (B) to red eyes (b). With this information, answer questions # What are the phenotypes of rabbits that have the following genotypes: Ggbb ggbb ggbb GgBb 2. Determine the gametes produced by a male rabbit with the genotype GgBb. 3. A male rabbit homozygous for grey hair and red eyes is crossed with a female rabbit that is white hair and heterozygous for black eyes. Set up a Punnett Square below that shows the possible offspring of these two rabbit parents. a) Draw a Punnett Square that shows all possibilities of this cross. Genotype Parent #1: Genotype Parent #2: b) Give all possible ratios for each genotype and each phenotype for the offspring of this cross. Genotype Phenotype Ratio Ratio c) Calculate the probability (%) that each genotype and phenotype will occur in the offspring. Genotype Phenotype Probability Probability

8 4. In sunflowers, being tall is dominant (T) over being short (t). Cross two heterozygous tall sunflower plants. Record the results in the table below for this monohybrid cross. a) Draw a Punnett Square for this cross. b) List all possible genotypes and phenotypes for the offspring of this cross. c) Give all possible ratios for each genotype and each phenotype. Genotypes Corresponding Phenotypes Genotype Ratio Phenotype Ratio 5. In humans, hairy knuckles is dominant (B) over smooth knuckles (b). When a male with hairy knuckles produces offspring with a female with hairy knuckles, their offspring were 75% hairy and 25% smooth. With this information, what is the genotype of the male and the genotype of the female? 6. A red carnation flower (RR) is crossed with a white carnation flower (rr). The resulting offspring are all pink. What would be the results of a cross between a white carnation flower and a pink carnation flower? In your answer include: Punnett Square showing the cross between Genotypic & Phenotypic Ratios the pink flower & the white flower. Probability of possible genotypes & phenotypes a) Draw a Punnett Square that shows all possibilities of this cross. b) Give all possible ratios for each genotype and each phenotype for the offspring of this cross. c) Calculate the probability (%) that each genotype and phenotype will occur in the offspring. Genotype Ratio Phenotype Ratio Genotype Probability Phenotype Probability

9 Introduction: Unit 8: GENETICS Virtual Lab: Punnett Squares A trait is a physical characteristic such as color or size that offspring inherit from parent(s). The genes that control a trait come in pairs, one gene from each parent. A combination of capital and lowercase letters are used to represent these gene pairs. For example: if one parent contributes a gene for blue eyes (b) and the other parent contributes a gene for brown eyes (B), then the offspring s genes for eye color are written as Bb. This combination of genes is called a genotype. Each letter in a gene pair stands for one form of the gene. The different versions of a gene are called alleles and are represented as a capital/lowercase letter. In this example, the alleles are blue eye color (b) and brown eye color (B). The two types of alleles are dominant and recessive. A dominant allele is written as a capital letter and a recessive allele is written as a lowercase letter. If a gene pair contains a dominant allele, then the dominant allele will be the allele that the offspring will express/show. Recessive alleles are only expressed when paired with another recessive allele. The physical characteristic that is expressed is called the phenotype. Punnett Squares are a way to determine the probability of offspring inheriting certain genes/alleles from parents. In this lab, you will use a Punnett Square to find possible gene combinations for Drosophila offspring. Objectives: 1. Make and defend a claim based on evidence that inheritable genetic variations may result from: combinations, replication & mutations. (HS-LS3-2) 2. Use Punnett square to predict the results of genetic crosses: mono & dihybrid (ratio & probability). (HS10-LS3-2.1) 3. Determine genotype and phenotype of a parent organism: heterozygous, homozygous. (HS10-LS3-2.2) 4. Determine genotype and phenotype of an offspring: heterozygous, homozygous. (HS10-LS3-2.3) 5. Explain Mendel s Principles of Genetics: Law of Segregation and Law of Independent Assortment. (HS10-LS3-2.4) Materials: Computer Lab Sheet Procedure: 1. Open Lab Notebook to the next available page. 2. Add the following title: Virtual Lab: Punnett Squares 3. List this lab in the table of contents. 4. Label the first section: Introduction 5. Cut out the Introduction & tape in under the title. 6. Read through the Introduction and highlight important information. 7. Label the next section: Data 8. Using a ruler, draw Table 1 in the Data section (enlarge if necessary). Table 1: Punnett Squares Data Genotype Scenario # Parent #1 Parent #2 Genotype Ratio Phenotype Ratio 9. Label the next section: Conclusions 10. Tape the Conclusion Questions in the Conclusion section. Leave room to answer the questions. 11. GET INSTRUCTOR INITIALS

10 AFTER getting instructor initials: 1. Get on the class website: thsclaybio.weebly.com 2. Click: Semester #2 3. Scroll to: Unit 8: Genetics section. 4. Click: Virtual Lab: Punnett Square button. 5. Read: Purpose and Objectives. 6. Follow the Procedure step by step (use earbuds for the short video). 7. Choose 3 different scenarios to experiment with. 8. Record any information in Table 1 in the Data section. 9. Answer the Conclusion Questions using complete sentences and include DETAILS! Conclusion Questions: 1. Select 1 monohybrid cross performed in this Investigation. Describe how to use the phenotype ratios to determine the percentage of offspring displaying each trait. In your response, make sure to include: generic math formula to find probability work that demonstrates how to use the formula 2. Can the genotype for a gray-bodied fly be determined? Why or why not? 3. Describe all of the possible genotypes for a fly with the phenotype mentioned in question #2. 4. In the instance of complete dominance, explain why an organism with a homozygous dominant genotype has the same phenotype as an organism with a heterozygous genotype. 5. What genetic information CAN be obtained from a Punnett Square? 6. What genetic information CANNOT be determined from a Punnett Square?

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