Midterm Questions 2015 draft 1

Midterm Examination questions, Winter 2015 [19 Feb 2015]

Instructions: Prepare answers for all questions. FOUR of these questions will be chosen at random for the midterm. Your may answer ANY TWO of these. You MAY NOT answer the question based on your group’s presentation. Answers should be no longer than one side of an 8.5x11 sheet; you may sketch an outline on the reverse. Answers will be graded on the expectation that you have written out answers to all questions ahead of time, and that the examination paper is only a check that this has been done.

1. What is a ‘gene’ in 2015? Describe the some of the differences between the concept of a gene as understood after cracking of the code in 1965 versus fifty years later in 2015.

2. Consider the hypothetical Luria-Delbruck experiments for the induction and mutation models. Calculate the mean and variance of each experiment after two further generations. How do the results relate to the statistical design of the experiment?

3. The Hershey & Chase (1952) experiment has been criticized as being "quick and dirty". In Figure 1 of the experiment, what result would you expect to obtain if all phage protein remained outside, and all phage nucleic acid went inside the bacterial cells? What are some explanations

4. Watson and (or) Wilkins have been criticized for miss-use of data from Franklin. Based on the evidence presented in lecture, to what extent is the criticism justified? Give the facts and explain your reasoning. Which is more critical to understanding the genetic properties of DNA, it’s double helical structure or specific base-pairing? Explain your reasoning.

5. Meselson & Stahl (1958) use analytical centrifugation to demonstrate the semi-conservative mode of DNA replication. Sketch the banding patterns that would be expected if DNA replication were conservative, or dispersive. At what stage of the original experiment can the conservative and dispersive models be ruled out? Explain.

6. McClintock (1953) cross analysis: Based on the genetics of the Ac-Ds system, explain the phenotypes of the three kernels.

7. King & Wilson performed four main calculations to show that chimps and humans were >99% genetically similar. (1) Review the assumptions and the calculation based on protein electrophoretic similarity S = 0.52. (2) repeat the calculation if S = 0.42 or 0.62

8. Nirenberg et al. (1965) deciphered the first four codons of the genetic code by use of poly U, C, A, and G, and a further set by use of all possible dinucleotide combinations (UA, UC, UG, CA, CG, AG, etc). (1) Show which additional codons can be deciphered by the use of dinucleotide polymer messages. What does this information indicate about degeneracy of the code? (2) Consider a poly-U message ‘spiked’ with small amounts of A, or C, or G: what additional codons, and what information about degeneracy would be shown?

9. Gill et al. (1914): What would the Romanovs and their doctors have known about the genetics of Hemophilia at the time of Tsarevitch Alexei's birth in 1904? Construct a family pedigree for the Tsar, Tsarina, and their five children, based on the information in Bogaev et al. (2009) [For grins, see Hay (1813)]