Offspring acquire genes from parents by inheriting chromosomes [2].

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1 GUIDED READING - Ch. 14 MENDEL & THE GENE IDEA NAME: Please print out these pages and HANDWRITE the answers directly on the printouts. Typed work or answers on separate sheets of paper will not be accepted. Importantly, guided readings are NOT GROUP PROJECTS!!! You, and you alone, are to answer the questions as you read. You are not to share them with another students or work together on filling it out. Please report any dishonest behavior to your instructor to be dealt with accordingly. Get in the habit of writing legibly, neatly, and in a NORMAL, MEDIUM-SIZED FONT. AP essay readers and I will skip grading anything that cannot be easily and quickly read so start perfect your handwriting. Please SCAN documents properly and upload them to Archie. Avoid taking photographs of or uploading dark, washed out, side ways, or upside down homework. Please use the scanner in the school s media lab if one is not at your disposal and keep completed guides organized in your binder to use as study and review tools. READ FOR UNDERSTANDING and not merely to complete an assignment. Though all the answers are in your textbook, you should try to put answers in your own words, maintaining accuracy and the proper use of terminology, rather than blindly copying the textbook whenever possible. 1. In the 1800s the most widely favored explanation of genetics was blending. [2] How does the blending hypothesis of inheritance differ from Mendel s particulate hypothesis of inheritance? Offspring acquire genes from parents by inheriting chromosomes [2]. 2. One of the keys to success for Mendel was using pea plants. Explain how using pea plants allowed Mendel to control mating; that is, how did this approach let Mendel be positive about the exact characteristics of each parent? [2]

2 3. Define the following terms. a. Character: b. Trait: c. True-breeding: d. Hybridization: e. P generation: f. F 1 generation: g. F 2 generation: 4. When considering your own family and thinking of the P, F 1, and F 2 generations. [2] a. which generation would your mom s grandparents be? b. which generation would your mom be? c. which generation would each parent be?

3 5. Explain how Mendel s simple cross of purple and white flowers did the following: [2] a. Refuted blending b. Determined dominant and recessive characteristics c. Demonstrated the merit of experiments that covered multiple generations 6. a. What is an allele? Briefly include an explanation of how one allele of a gene differs from another allele for that same gene as far as the DNA is concerned. b. Think: How many alleles of a gene are found on an individual chromosome? c. Think: What is the maximum number of alleles of a particular gene that can be found in the DNA of an individual human? Explain. d. Think: Is the number mentioned in question 6.c. the same as the maximum number of alleles that could exist in the DNA of the entire population? Explain. (See page 273).

4 e. What is a locus (loci plural)? f. Think: Would the various possible alleles of a gene be located at different loci or the same locus? 7. On the figure below, label the allele for both purple and white flower color, a homologous pair, and the locus of the flower color gene. [2] 8. In sexually reproducing organisms, why are there exactly two chromosomes only in each homologue group? [2] 9. What is the difference between a dominant and recessive allele as far as an organisms appearance is concerned? 10. In your own words, what is Mendel s Law of Segregation? [3]

5 11. Mendel s model consists of four main concepts as you have read. For review, name and describe each concept. Indicate which of the concepts can be observed during meiosis by placing an asterisk next to the concept name and description. [2] 12. Define the following a. Punnett Square: b. Homozygous: c. Heterozygous: d. Phenotype: e. Genotype:

6 13. Using Figure 14.5 as your guide, provide the missing notations for the figure below (P, F 1, F 2 ), fill in the missing genotype of the games involved, and answer the following questions. [2] a. What is the F 2 phenotypic and genotypic ratio? b. Which generation is completely heterozygous? c. Which generation has both heterozygous and homozygous offspring? Why? 14. A pea plant heterozygous for inflated pods (Ii) is crossed with a plant homozygous for contricted pods (ii). Draw a Punnett square for this cross. Assume pollen comes from the ii plant. [1] 15. a. What is a test cross and why is it useful? b. Practice: Explain how a test cross would be conducted in order to determine if a pea plant exhibiting inflated pods is homozygous or heterozygous if the inflated pod allele I is dominant to constricted pod allele i.

7 c. Practice: What proportion of offspring should exhibit inflated pods if the pea plant from 14.b. is a homozygote versus if this pea plant turns out to be a heterozygote? 16. a. Define the terms monohybrid and dihybrid. b. Give an example of a monohybrid cross and a dihybrid cross. [3] 17. a. What is the Law of Independent Assortment? b. Relate your knowledge: How does this law relate to meiosis? [3] c. Why does this law apply to genes located on different chromosomes more so than those located on the same chromosome? [3]

8 18. As you start to work word problems in genetics, two things are critical: the parent s genotype must be correct, and the gametes must be formed correctly. Using Figure 14.8 as your guide, explain how the gametes are derived for the following cross. (You should have four different possible gametes). YyRr YyRr 19. a. Complete the cross given in questions 17 by placing the gametes in a Punnett square. [2] b. Then provide the phenotypic ratio of the offspring. [2] 20. a. Pea plants heterozygous for flower position (axial vs terminal) and stem length (tall versus dwarf), AaTt, are allowed to self-pollinate, and 400 of the resulting seeds are planted. Draw a Punnett square for this cross. b. How many offspring would be predicted to have terminal flowers and be dwarf? See table [1] 21. a. List the different gametes that could be made by a pea plant heterozygous for seed color, seed shape, and pod shape (YyRrIi). See Table b. How large a Punnett square would you need to predict the offspring of a self-pollination of this trihybrid?

9 Offspring acquire genes from parents by inheriting chromosomes [2]. 22. An event that is certain to occur has a probability of, while an event that is certain not to occur has a probability of. [2] 23. a. First define and then explain, in your own words, when you use the Multiplication Rule. [2] b. Give an original example not from the textbook. [1] c. Next define and then explain, in your own words, when you use the Addition Rule. [2] d. Give an original example not from the textbook. [1] 24. What is the probability that a couple will have a girl, a boy, a girl, and a boy in this specific order? Show work. 25. a. Practice: What is the probability that a heterozygote for green pod color (Gg) produces gametes with allele G? b. Practice: What is the probability that a heterozygote for green pod color (Gg) produces gametes with allele g? c. Practice: What is the probability that two G alleles will be present in the gametes at fertilization? (show your calculation) 26. What is the probability that a couple will have a girl, a boy, a girl, and a boy in this specific order? Show work. 27. a. What proportion of offspring form a CCxCc cross are expected to be homozygous dominant? Show work. [1] b. Homozygous recessive? c. Heterozygous?

10 28. a. An organism with the genotype BbDD is mated to one with the genotype BBDd. Assuming independent assortment of these two genes, write the genotypes of all possible offspring from this cross. [1] b. Use the rules of probability to calculate the chance of each genotype occurring. Show work. [1] 29. Practice: A dihybrid cross is conducted between two heterozygotes for green pod color and round seed shape (GgRr). What fraction of offspring would be predicted to exhibit the recessive phenotype for at least 1 character? (Show your calculation) 30. Practice: Three characters (flower color, seed color, and pod shape) are considered in a cross between two pea plants PpYyIi x ppyyii. What fraction of offspring would be predicted to be homozygous recessive for at least two of the three characters? [1] Inheritance patterns are often more complex than predicted by simple Mendelian genetics [2]. Inheritance patterns are often more complex than predicted by simple Mendelian genetics. In Mendel s pea plants, each character is determined by one gene only and there are only two possible alleles (variations), one completely dominant and one completely recessive. However, alleles are not always completely dominant or recessive, many times a gene may have more than just two possible alleles, or one gene could produce multiple phenotypes. 31. a. Contrast complete dominance and incomplete dominance.

11 b. Give an example of incomplete dominance. [2] 32. a. Compare and contrast codominance with incomplete dominance. [2] b. Give an example of codominance. 33. Why does the determination of an allele as dominant or recessive depend on the level (organismal, biochemical, & molecular) at which we examine phenotype? 34. Does having a dominant allele mean that it will be found in greater frequency in the population? Why? [3]

12 35. a. A rooster with gray feathers is mated with a hen of the same phenotype. Among their offspring, 15 chicks are gray, 6 are black, and 8 are white. What is the simplest explanation for the inheritance of these colors in chickens? b. What phenotypes would you expect in the offspring of a cross between a gray rooster and a black hen? Why? 36. Explain what is meant when a gene is said to have multiple alleles? [2] 37. How is the ABO blood group in humans determined by multiple alleles? 38. Blood groups are so important medically that you should be able to solve genetics problems based on blood types. The first step in accomplishing that is to understand the genotypes of each blood type. Before working any problems, complete this ABO blood type chart. [2] 39. Practice: If a man with type AB blood marries a woman with type O blood, what blood types would you expect in their children? [1]

13 40. a. Define the term pleiotropy. b. Explain why this is important like cystic fibrosis and sickle-cell disease. 41. a. In your own words, explain epistasis. b. How do mice exhibit epistasis in reference to coat color? c. Explain why the dihybrid cross detailed in Figure has 4 white mice instead of the 3 that would have been predicted by Mendel s work. 42. a. What is polygenic inheritance? b. What would be your clue that a character would have a polygenic inheritance pattern? [3] c. What are some examples of quantitative characters that exhibit polygenic inheritance. 43. a. What does it mean when geneticists say that a phenotype is multifactorial?

14 b. Use the terms norm of reaction and multifactorial, explain the potential influence of the environment on phenotypic expression. Many human traits follow Mendelian patterns of inheritance [2]. 44. What is a pedigree? 45. What is a carrier? 46. a. Pedigree analysis is often used to determine the mode of inheritance (dominant or recessive, for example). Be sure to read the Tips for pedigree analysis in Figure 14.15; then complete the unlabeled pedigree by indicating the genotypes for all involved [2] trying NOT to copy the book See if you can get it right. b. What is the mode of inheritance for this pedigree? [2]

15 c. Explain why you know the genotype of one female in the third generation but are unsure of the other? [2] 47. Describe what you think is important to know medically about the behavior of recessive alleles. [2] AP Students are expected to have a general knowledge of the pattern of inheritance and the common symptoms of a number of genetic disorders. [2] Do not ignore information on inheritance patterns of diseases discussed in your text. 48. Describe and discuss the genetics of the following inherited disorders: a. Cystic Fibrosis b. Sickle cell disease:

16 c. Achondroplasia: d. Huntington s disease: 49. Think: Joan was born with six toes on each foot. Two of her five siblings and her mother, but not her father, also have extra digits. What is Joan s genotype for the number-of-digits character? Explain using D and d to symbolize the alleles for this character. [1] 50. Think: Beth and Tom each have a sibling with cystic fibrosis, but neither Beth nor Tom nor any of their parents have the disease. [1] a. Calculate the probability that if this couple has a child, the child will have cystic fibrosis. b. What would be the probability if a test revealed that Tom is a carrier but Beth is not?

17 51. What would you suspect if Peter was born with polydactyly, but neither of his biological parents had extra digits? 52. Amniocentesis and chorionic villus sampling are the two most widely used methods for testing a fetus for genetic disorders. a. Briefly contrast amniocentesis and chorionic villus sampling. b. Use the unlabeled diagram below to explain the three main steps in amniocentesis and the two main steps of CVS.

18 53. What are the strengths and weaknesses of each fetal test? [2] 54. Explain the symptoms of phenylketornuria, and describe how newborn screening is used to identify children with this disorder. References 1. Campbell et al. (2008). AP* Edition Biology. 8th Ed. San Francisco: Pearson Benjamin Cummings. 2. Adapted from Fred and Theresa Holtzclaw 3. Adapted from L. Miriello