Biol4241 - Midterm Questions 2012

Bio4241 - Midterm exam questions
Exam: Wednesday, 29 February, 2-3P [1 hour exam]

Instructions:
1. Prepare answers for all of the assigned midterm essay questions.
2. Your answer for each should fit on the front and back of one lined sheet of paper.
3. For the exam, I will select at random four questions. Answer any two of these. (You may not answer the question pertaining to your own group's presentation).
4. You may bring notes on your prepared answers, on the front and back of one 8.5 x 11 sheet of paper. [Please don't try to cram complete essays onto this page!].
5. You will have one hour to answer the two questions.

SMC1: What is a Gene? How would you define the concept "gene" in 2012? Compare and contrast your definition with the “gene” as it was understood by the time of the “cracking of the genetic code” ca. 1965.

SMC2: Suppose that the Luria & Delbruck (1941) thought experiment for the mutation hypothesis
    [ http://www.mun.ca/biology/scarr/4241smc_Luria-Delbruck_TE2.html ]
    were continued for two more generations beyond what is shown, and that a mutation occurs in one cell of culture #4 in the next-to-last generation.
    Calculate the expected mean and variance among cultures in the final generation, and the mutation rate.

Group 1. The Hershey & Chase (1952) experiment is often presented in an oversimplified manner in introductory textbooks.
    Identify at least three oversimplifications in the illustration at [ http://www.mun.ca/biology/scarr/Hershey_Chase_Experiment2.html ].
    Draw the graph for the blender experiment [ http://www.biol4241.com/id75.html ] if the ideal result had been obtained.

Group 2. Sketch the expected ultracentrifuge results from the Meselson & Stahl (1958) experiment [ http://www.biol4241.com/id102.html ]
    if DNA replication were (1) conservative or (2) dispersive. Describe a specific mode for dispersive replication.
    If DNA were replicated conservatively, predict the effect on Mendel’s Rules.

Group 3. Following up on the work of Garapin et al. 1978, Smith & Jones 2012 isolated the gene for ovalbumin from the platypus. From a cDNA copy of the mRNA, they did a set of restriction digests with the endonucleases A, B, & C, singly and in pairwise combination: these data are show in the left-hand box. They did the same digests on a clone of the genomic DNA (gDNA), and obtained the results in the right-hand box.

1. How many introns are present? What are their sizes?
2. Draw a restriction map that locates the introns in the map of A B C
3. Draw the expected results when the cDNA is annealed to the gDNA
4. HINT: tba

intron exon
data

Group 4: Refer to the summary of Table 3 in McClintock 1953 [http://biol4241.com/id124.html]. Explain how the concept of graded potential of Ac activator explains the difference between the 1:1 and 6:1 experimental ratios in the first block.

Group 5: King & Wilson 1975 used four types of data to estimate the genetic similarity of chimps and humans. Summarize the calculations for protein electrophoresis and show how number 99.18% similarity was obtained from the data.

Group 6: Sanger et al. 1977 used cloned DNA, southern-blot probes, auto-radiography, and PAGE to determine the order of bases in DNA sequences. Compare and contrast these techniques with those used in current dideoxy-based automated sequencing machines.

Group 7: Jeffreys et al. 1985 included DNA "fingerprint" comparisons among sib-sib and parent-offspring pairs. Because full sibs and parent-offspring are both related by 0.5, they are expected to share one-half of their alleles over a number of loci. Is it possible to distinguish a mother-son pair versus a brother-sister pair by DNA fingerprinting? Explain.

Consider a case where the mother has alleles AB at each of four loci (A1 / B1 through A4 / B4), and her son and daughter between them show combination of four alleles ABCD at all four loci (A1, B1, C1, D1, etc.). (The father's fingerprint is unknown). What mother-offspring and sib-sib genetic combinations are possible? Is there a rule by which the two patterns are genetically distinguishable?

Group 8: The title of the paper by Rothenberg et al. 2010 emphasizes that their detection system is "non-optical", which is said to give more reliable results than conventional dideoxy-based systems. Explain non-optical sequence detection, and comment on its accuracy relative to current automated sequencing.