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Unformatted text preview: Genetics 380, Spring 2009 Examination #1A ANSWERS A different textbook and a different set of topics was covered last year on exam 1. Therefore, ignore questions 7 and 8, since they will be on exam 2 this year. Study the remaining 8 questions and the Bonus question. I have added a question from exam 2 last year and its answer based on Ch.6 (DNA Replication) at the bottom. This material will be on exam 1 this year. 1. ( 7 pts ) Consider a diploid organism with 3 pairs of chromosomes (A, B and C from the mother and A, B and C from the father). While answering the questions below, assume that no crossing-over occurs during meiosis. (2 pts) What proportion of gametes would only have maternal chromosomes (A, B and C)? 1/2 x 1/2 x 1/2 = 1/8 (No partial credit) (5 pts) What proportion of gametes would have chromosomes inherited from both mother and father? 1/8 father only; 1/8 mother only (see part a above) 6/8 from both parents 2. (8 pts ) In a human male, from which grandparent could each sex chromosome have been inherited? (Indicate yes or no for each option) Mothers Mothers Fathers Fathers Mother Father Mother Father X-chromosome Yes Yes No No Y-chromosome No No No Yes Labeling all 8 chromosomes- 1, 2 (X-chromosomes of maternal grandmother) 3 (X-chromosome of maternal grandfather) 4 (Y-chromosome of maternal grandfather) 5, 6 (X-chromosomes of Paternal grandmother) 7 (X-chromosome of paternal grandfather) 8 (Y-chromosome of paternal grandfather) Mother is (1 or 2 + 3) Father is (5 or 6 + 8) Grandchild is (1 or 2 or 3 from mother) and (8 from father) 3. ( 10 points ) In Mangoes, Red fruit (R) is dominant over Yellow (r), and Juicy fruit (J) is dominant over Fibrous (j). Given below are the phenotypes of the parents and their progeny. Determine the genotypes of the parents in each cross. (a) Red Juicy x Red Fibrous gives 3/8 Red Juicy; 3/8 Red Fibrous; 1/8 Yellow Juicy and 1/8 Yellow Fibrous. _ RrJj __ X _ Rrjj __ (b) Red Fibrous x Red Fibrous gives 3/4 Red Fibrous and 1/4 Yellow Fibrous. _ Rrjj __ X _ Rrjj _ 4 . ( 12 points ) In Mangoes, Red fruit (R) is dominant over Yellow (r), and Juicy fruit (J) is dominant over Fibrous (j). A true-breeding Red Juicy plant is crossed to a true breeding Yellow Fibrousover Fibrous (j)....
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- Spring '08