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Chapter 11 Teacher Guide and Answers Diagnostic Test • Student thinks both A and B are recessive. Direct student to discussion on multiple alleles in Section 2. • Student thinks blood types differ among people with an allele for both A and B blood types. Direct student to the multiple alleles discussion in Section 2. Page 39 1. The correct answer is B. Based on student responses, use the list below to address preconceptions. • Student thinks that there are no diseases or disorders caused by heredity. Direct student Launch Lab to the recessive genetic disorders discussion in Section 1. Page 40 • What do you know about human • Student thinks recessive genes cause all genetic inheritance? disorders. Direct student to the dominant Analysis genetic disorders discussion in Section 1. 1. Answers will vary, but should give some • Student thinks dominant genes cause all insight into the knowledge, background, and genetic disorders. Direct student to the recessive experiences your students have regarding genetic disorders discussion in Section 1. human heredity. Identify and correct any • Student thinks environmental factors cause misconceptions. albinism. Direct student to the recessive genetic 2. Knowledge of human heredity is necessary to disorders discussion in Section 1. understand legal, social, and moral issues that • Student thinks dietary factors cause albinism. involve inherited traits. Such knowledge could Direct student to the recessive genetic disorders help with making certain health decisions. discussion in Section 1. 2. The correct answer is C. Based on student responses, use the list below to address preconceptions. • Student thinks a pedigree catalogs all observable traits of a person. Direct student to the pedigree discussion in Section 1. • Student thinks a pedigree traces all the observable traits through a family’s history. Direct student to the pedigree discussion in Section 1. • Student thinks a pedigree only involves the family history of royalty or famous people. Direct student to the pedigree discussion in Section 1. • Student thinks a pedigree maps the genetic makeup of a person. Direct student to the pedigree discussion in Section 1. 3. Neither A nor B is dominant. The two blood types are codominant, which means that both alleles are expressed. Based on student responses, use the list below to address preconceptions. • Student thinks either A or B is the dominant allele. Explain to student that both blood types are dominant because both alleles are expressed. The alleles are codominant. Unit 3 MiniLab Page 41 • Investigate Human Pedigrees Analysis 1. With pedigrees, it is easy to follow traits from one generation to the next. 2. Families affected with unfavorable traits can be given advice about the chances of their future children possessing these traits. However, pedigree information obtained from only a few members of a family could be inaccurate, unreliable, or misleading. Minilab Page 42 • Explore the Methods of the Geneticist Analysis 1. Answers will vary. Sample answer: We look for the ratio of hitchhiter’s thumbs to non-hitchhiter’s thumbs. 2. Students might suggest DNA analysis or compiling pedigrees to determine dominance. In small populations, traits can be more common even though they are recessive, which might cause students to misidentify them as dominant. CHAPTER 11 TEACHER GUIDE AND ANSWERS 155 Chapter 11 Teacher Guide and Answers Part B • Ask students “How is genetic engineering similar Page 43 • What’s in a face? Investigate Inherited to selective breeding?” “In what ways is genetic Human Facial Characteristics engineering different from what has been practiced Analyze and Conclude as selective breeding?” Discuss the concept of unintended outcomes, and elicit some examples from 1. The male determines the gender of the offspring students’ everyday experiences and observations. in humans. • Ask students to interview their parents or other 2. a 50 percent chance in each situation older relatives or friends about what they remem3. To achieve this outcome, both parents must have ber about thalidomide babies or DDT. Have stuwavy hair (Hh). dents share their findings. Discuss the intended 4. Answers will depend on the traits used. purposes of the substances and their unintended 5. The chances of two groups producing identical outcomes. Extend these concepts to the informaoffspring are quite remote. It would require each tion provided in the table in this activity. coin flip for each group to be exactly the same • Below Level: (1) Provide an audiotape of the text to for each trait. which students can listen while reading the activity. (2) Laminated cutouts of the ears of corn and the Real-World Biology: Analysis corn plants in the different sizes and conditions of “robustness” can be provided as manipulatives to Page 45 • Improving Food Crops aid in understanding the hybridization process. Planning the Activity • Above Level: Have students choose an issue or a This activity may be used with the study of genetproblem from the table, plan a study of the probics to reinforce and extend the concepts of selective lem, and explain how data will be collected and breeding and genetic engineering. analyzed. Purpose Answers to Student Worksheet Students examine methods and effects of selective Part A: Hybrid Vigor breeding and genetic engineering. BioLab Career Applications Many agricultural technicians work under the guidance of agricultural scientists as they conduct tests and experiments to improve the yield and quality of crops or to increase the resistance of plants and animals to disease, insects, or other hazards. In some cases, technicians use computers and computer-interfaced equipment extensively during their research. In other cases, technicians perform much of their work outdoors, sometimes in remote locations. Teaching Strategies Part A Introduce the concept of selective breeding by eliciting from students information about what they know about pedigreed animals. What does pedigree mean? Do students own a pedigreed dog or cat? If so, what are the animal’s characteristics? Which are the most desirable? 156 CHAPTER 11 TEACHER GUIDE AND ANSWERS Analyze and Conclude 1. Two inbred strains, A and B, are crossed with each other to produce a hybrid A × B plant. Two other inbred strains, C and D, are crossed with each other to produce a hybrid C × D plant. Then plants A × B and C × D are crossed to produce a double hybrid (A × B) × (C × D) plant. 2. larger ears of corn and taller plants Part B: Genetically Engineered Foods Analyze and Conclude 1. Scenarios will vary, but should be based on current evidence and employ logical reasoning. Careers in Biology Agricultural technicians conduct research, tests, and experiments to improve the yield and quality of crops or to increase the resistance of plants and animals to diseases, insects, or other hazards. Unit 3 Chapter 11 Teacher Guide and Answers Enrichment Page 47 • Blood Typing in Forensic Science System Groups Frequency in the General Population (average) ABO A, B, AB, O A AB = = 40% 5% B O = = 10% 45% Rh Rh+, Rh– Rh+ = 85% Rh– = 15% MN M, N M = 50% N = 50% Lewis Le(a+b–), Le(a– b+), Le(a+b+), Le(a–b–) Le(a+b–) Le(a+b+) = = 22% 6% Le(a–b+) Le(a–b–) = = 72% ~0% Cartwright Yta, Ytb Yta = 99% Ytb = 1% Student calculations will differ depending on the blood systems chosen and the blood groups assigned to the individual for whom the calculation is performed. Concept Mapping Page 48 • Genetic Disorders 1. a dominant gene 2. nondisjunction 3. albinism 4. Huntington’s disease 5. too many 6. Down syndrome 7. Turner’s syndrome Study Guide Page 49 • Section 1 1. pedigree 2. alleles 3. homozygous 4. alleles 5. heterozygous 6. dominant 7. recessive 8. cystic fibrosis or albinism 9. albinism or cystic fibrosis Unit 3 Students will discover that the frequency of blood groups might differ among different populations. The numbers given in the above table are rough estimates for the American Caucasian population. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. albinism galactosemia Tay-Sachs disease cystic fibrosis Huntington’s disease achondroplasia true false false true true recessive They are carriers. There has to be at least one dominant gene. Page 51 • Section 2 1. The check should be in the far right cell. 2. The check should be in the middle cell. 3. The check should be in the far left cell. 4. no 5. no 6. male CHAPTER 11 TEACHER GUIDE AND ANSWERS 157 Chapter 11 Teacher Guide and Answers Page 52 • Section 3 1. A 2. D 3. E 4. B 5. C 6. There are two copies of chromosome 20. 7. There are three copies of chromosome 21. 8. There are two copies of chromosome 22. 9. It has a set of three chromosomes of one kind. 10. nondisjunction 11. older Guía de estudio Página 53 • Sección 1 1. pedigrí 2. alelos 3. homocigoso 4. alelos 5. heterócigo 6. dominante 7. recesivo 8. fibrosis quística o albinismo 9. albinismo o fibrosis quística 10. albinismo 11. galactosemia 12. enfermedad de Tay-Sachs 13. fibrosis quística 14. enfermedad de Huntington 15. acondroplasia 16. verdadero 17. falso 18. falso 19. verdadero 20. verdadero 21. recesivo 22. Son portadores. 23. Tiene que haber al menos un gen dominante. 158 CHAPTER 11 TEACHER GUIDE AND ANSWERS Página 55 • Sección 2 1. Se debe marcar la celda de la extrema derecha. 2. Se debe marcar la celda del medio. 3. Se debe marcar la celda de la extrema izquierda. 4. no 5. no 6. hombre Página 56 • Sección 3 1. A 2. D 3. E 4. B 5. C 6. Hay dos copias de cromosoma 20. 7. Hay tres copias de cromosoma 21. 8. Hay dos copias de cromosoma 22. 9. Tiene un conjunto de tres cromosomas de una clase. 10. no disyunción 11. mayores Section Quick Check Page 57 • Section 1 1. Student answers will vary. Answers might include three of the following recessive genetic disorders: cystic fibrosis, albinism, Tay-Sachs disease, galactosemia, and sickle-cell anemia. 2. A pedigree is a diagram that traces the inheritance of a particular trait through several generations. 3. CC is homozygous dominant, Cc is a carrier, and cc is heterozygous recessive. The individual with the cc genotype will have cystic fibrosis. 4. Their offspring will not express the recessive trait because both parents must be carriers (have at least one recessive allele) to produce offspring with two recessive alleles. 5. Huntington’s disease is not lethal until after reproductive age, so individuals can pass on the allele to their children before they have symptoms. Unit 3 Chapter 11 Teacher Guide and Answers Page 58 • Section 2 1. Codominance happens when both alleles are expressed in the heterozygous condition. 2. Coat color of rabbits is determined by multiple alleles. 3. Certain phenotypes or disorders that are inherited can be affected by environment. Student examples will vary, but might include that the tendency to develop heart disease is inherited, but the occurrence and seriousness of the disease are affected by diet and exercise. 4. With multiple alleles, more than two alleles are possible for one pair of genes. For polygenic traits, multiple alleles interact in multiple pairs of genes. 5. For a woman to be color blind, the mother must be a carrier or homozygous color blind, and the father must be color blind. Because color blindness is rare, it would be rare for two such people to meet and have children. Page 59 • Section 3 1. Down syndrome is usually caused by three copies of chromosome 21. 2. A telomere is a protective cap that is found on the end of chromosomes and consists of DNA associated with proteins. 3. A karyotype is a micrograph in which pairs of homologous chromosomes are arranged in decreasing size. 4. Genotype XXX contains three copies of the X chromosome, so it is trisomy. 5. Amniocentesis samples the fluid surrounding the fetus for various chemicals and tests for certain genetic disorders. Chorionic villus sampling samples placenta tissue to test for chromosomal abnormalities. Chorionic villus sampling can be done earlier in the pregnancy but might not reveal problems with metabolism and is less accurate than amniocentesis. Chapter Test A Page 60 • Part A: Multiple Choice 1. C 2. D 3. B Unit 3 Page 60 • Part B: Matching 1. B 2. C 3. A Page 61 • Part C: Interpreting Pedigrees 1. The Roman numerals represent successive generations. 2. one 3. The pedigree illustrates a dominant genetic disorder. 4. The black circle could represent a female that is either heterozygous or homozygous for the disorder. Page 62 • Part D: Short Answer 1. Many inherited traits involve two forms of alleles for a trait, but human blood types have three forms of alleles including O, A, and B. Different combinations of these alleles create several different blood types. 2. Sex-linked traits are controlled by genes located on the X chromosome. Males have one X chromosome, and females have two X chromosomes. As a result, males are affected by sexlinked traits more often than females. Page 62 • Part E: Concept Application 1. Cystic fibrosis is a recessive genetic disorder. For the outward expression of the disorder to express itself, a person must have two alleles for the disease. A carrier of the disorder will not express the disease outwardly but will carry one allele for the disorder. 2. The statement is incorrect. Down syndrome cannot be cured because the disease is a result of a mutation in the chromosomes of the individual. An extra chromosome 21 is the cause of Down syndrome, and it is currently impossible to remove that chromosome from every cell. Chapter Test B Page 63 • Part A: Multiple Choice 1. D 2. A CHAPTER 11 TEACHER GUIDE AND ANSWERS 159 Chapter 11 Teacher Guide and Answers 3. B 4. B Page 63 • Part B: Matching and Completion Matching 1. E 2. F 3. B 4. A 5. C Completion 6. carrier 7. incomplete dominance 8. epistasis 9. autosomes 10. polygenic traits Page 64 • Part C: Interpreting Pedigrees 1. Both parents are carriers of the disease and are heterozygous for Tay-Sachs disease. 2. The children would either be homozygous for not having the gene or heterozygous carriers of the disease. 3. II3 and II6 4. The first-generation female must be heterozygous for the disorder. If the female were homozygous for the disorder, all her children would express the disorder because it is a dominant genetic disorder. Page 65 • Part E: Concept Application 1. By analyzing the pedigrees of both families, the Tay-Sachs trait can be studied, and a genetic counselor can try to infer the genotypes of each set of parents from the observation of the phenotypes of family members. The genetic counselor can help the couple determine whether the inheritance pattern for the disorder is dominant or recessive, and the genotypes of the man and woman can be determined. The couple can use this information to decide whether or not they want to have biological children. 2. The statement is incorrect. Red-green color blindness is a recessive X-linked trait. Because males have only one X chromosome, they are more likely to be colorblind because only one recessive allele for the trait will cause the disorder to be outwardly expressed. Females have two X chromosomes, and a female must have two recessive alleles for the trait to be outwardly expressed. This condition is less likely, but it does occur. Chapter Test C Page 66 • Part A: Multiple Choice 1. A 2. C 3. C 4. A 5. D 6. D Page 65 • Part D: Short Answer 1. The genotypes are homozygous recessive (cc) Page 66 • Part B: Completion and heterozygous (Cc). The phenotype of a per1. carrier son who is homozygous recessive is the presence 2. incomplete dominance of all sickle-shaped red blood cells, while the 3. Epistasis phenotype of a person who is heterozygous for 4. polygenic traits the disorder will have both normal-shaped and 5. concordance rate sickle-shaped red blood cells. 6. fetal blood sampling 2. Blood types are determined by the multiple alleles A, B, and O. Blood type A has A markers, Page 67 • Part C: Interpreting Pedigrees blood type B has B markers, and blood type O 1. II1: homozygous for not carrying the Tayis the absence of either A or B markers. When Sachs disease gene; II2: heterozygous carrier of the A and B markers are codominant, they form the disease; II3: homozygous for not carrying blood type AB. the Tay-Sachs disease gene; II4: heterozygous carrier of the disease. 160 CHAPTER 11 TEACHER GUIDE AND ANSWERS Unit 3 Chapter 11 Teacher Guide and Answers 2. One-fourth of children will be homozygous for the disease, ½ of the children will be heterozygous carriers of the disease, and ¼ will be homozygous for not carrying the Tay-Sachs disease gene. The phenotypes would be ¼ of the children would outwardly express the gene and ¾ would not express the gene. 3. I2: heterozygous dominant; II2: heterozygous dominant; II3: homozygous recessive; II4: heterozygous dominant 4. The genotypes would be: ¼ homozygous dominant, ½ heterozygous dominant, and ¼ homozygous recessive. The phenotypes would be ¾ of the children would outwardly express the gene, and ¼ would not express the gene. Page 68 • Part D: Short Answer 1. By analyzing a family’s history, the trait of a genetic disease can be studied, and a genetic counselor can try to infer the genotypes of a person’s parents from the observation of phenotypes of family members. The genetic counselor can help the patient determine whether the inheritance pattern for the disorder is dominant or recessive, and the genotype of the individual can be determined. 2. Both X and Y chromosomes are sex chromosomes. The X chromosome is larger and contains genes essential for the development of both males and females. The Y chromosome primarily contains genes necessary for the development of male characteristics. Page 68 • Part E: Concept Application 1. The inheritance pattern is called codominance. All the offspring have an allele for red hair and an allele for white hair, and the traits of both alleles are expressed. In a codominant inheritance pattern, there is no recessive allele. 2. Both parents could be homozygous or heterozygous for type A blood. Another possibility is that one parent could be homozygous or heterozygous for type A blood, and the second parent could have type O blood. Unit 3 CHAPTER 11 TEACHER GUIDE AND ANSWERS 161