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Western University
Biology 2581B
Jim Karagiannis

SURNAME / INITIALS ____________________ (Please Print) Biology 2581b FIRST MIDTERM TEST Feb 5, 2011 - 9am -12 noon Version 222 25% of Final Mark 3 hours INSTRUCTIONS This test paper is composed of 40 equally weighted questions covering 17 sides (excl. cover). The last page contains a table of critical chi-square values. Please ensure that the exam is complete. Although there are no deliberate tricks on this paper there is ample opportunity to make careless oversights; READ THE QUESTIONS CAREFULLY. Answers will be subject to computerized matching analysis to detect cheating. Since it is impossible to provide equal access to instructors during the Test, proctors will NOT answer questions of interpretation. All answers must be recorded on the Scantron sheets within the 3 hour time limit. 1. Fill in your NAME at the top of the scantron sheet and the exam paper 2. STUDENT NUMBER - Print the digits of your student number in the squares provided. Mark the corresponding bubble in the column below each printed digit. 1 3. SECTION AND ANSWER SHEET - Leave these areas blank. 4. In the EXAM CODE section enter 222 5. Mark one choice from the alternatives provided for each question. 6. Submit your test paper and the Scantron sheet SEPARATELY. 1. Consider a long, linear molecule of dsDNA, one end of which is rotated six times with respect to the other end introducing negative (-) writhe. The two ends are then joined together to create a covalently closed circle. Which of the following statements concerning this molecule are true? i) The molecule is underwound. ii) The molecule is storing positive superhelical energy iii) The molecule would form positive supercoils. iv) The molecule is in an unfavourable state to promote transcription. A. Only i) is true. B. Only ii) is true. C. Only i), ii), and iv) are true. D. All are true. E. None are true. 2. Which of the following is not true of histones? A. They are rich in positively charged amino acids B. They are associated with the nucleosome. C. H2A, H2B, H3 and H4 form the nucleosome core. D. They are found in the nucleus. E. A complex of H1 and H2A help keep DNA properly wound around the nucleosome core. 3. Suppose that pigmentation in rabbits is controlled by two genes (E and H). Each gene exhibits complete dominance, and the relationship between genotypes and phenotypes are listed below: Genotype Phenotype E-H- albino eeH- brown E-hh albino eehh albino 2 What phenotype ratio would be expected among the progeny of a cross between dihybrid rabbits? A. 9 albino : 7 brown B. 9 brown : 7 albino C. 3 brown : 1 albino D. 13 brown : 3 albino E. 13 albino : 3 brown 4. In a linear eukaryotic chromatin sample, which of the following is formed into radial loops that are attached to the central scaffold? A. DNA without any attached histones. B. DNA in a complex with H1 only. C. The 10 nm fiber. D. The 30 nm fiber. E. None of the above. 5. Which of the following statements regarding the double strand break repair model of recombination are true? i) recombination is initiated by a double stranded break in one chromatid ii) recombination events can occur anywhere along the DNA molecule iii) resolution of Holliday junctions in the same plane results in an aborted crossover iv) branch migration can result in the creation of heteroduplex regions ranging from tens to thousands of base pairs. A. Only i) is true. B. Only i) and ii) are true. C. Only i), ii) and iii) are true. D. All are true. E. None are true. 6. The sequence of a mature mRNA is 5-AUCAAAUGGACUUUG-3. What is the corresponding sequence of the template strand of the gene encoding this message? A. 5-ATCAAATGGACTTTG-3 B. 3-ATCAAATGGACTTTG-5 C. 5-TAGTTTACCTGAAAC-3 D. 3-TAGTTTACCTGAAAC-5 E. 3-AUCAAAUGGACUUUG-5 7. Which of the following statements regarding double stranded DNA is true? i) The angle between the glycosidic bonds of the minor groove is 240 degrees. ii) G = C in each individual strand of DNA within the double helix 3 iii) The Z form of DNA is a right-handed helix iv) The B form of DNA does not exist in living organisms. A. Only i) is true. B. Only ii) is true. C. Only iii) is true. D. All are true. E. None are true. 8. Consider a fully heterozygous flowering plant with normal blue flowers and round seeds. This plant, when crossed with one that has red flowers and oval seeds, results in the following progeny: 91 blue, round 92 red, round 93 blue, oval 94 red, oval What is the recombination frequency? A. 0% B. 25% C. 33% D. 50% E. None of the above. 9. Out of 800 progeny of a three-point testcross there were 12 double crossover recombinants, whereas 20 had been expected on the basis of no interference. The interference is A. 0.05 B. 0.10 C. 0.20 D. 0.30 E. 0.40 10. In his experiments examining recombination of the car and Bar loci in Drosophila melanogaster, Curt Stern demonstrated that 4
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