Humboldt State University ® Department of Chemistry

Richard A. Paselk

 Chem 432

 Exam II


 Spring 1996

 (100 pts)

(13) 1 a. Sketch a tRNA molecule, indicating base paired regions. Label your diagram showing the names of the different arms/loops, the location of aa attachment, and the anticodon.


b. Describe this molecule in terms of its classification into 1°, 2°, and 3° levels of structure.


(10) 2. Describe the sequence of events whereby eukaryotic RNA transcripts are made into mRNA molecules. Where do these events take place?


(10) 3 a. What do we mean when we say the genetic code is "conservative"?


b. What is "wobble" and what has it to do (if anything) with the conservative nature of the code?


(15) 4. a. Diagram the replication fork in E. coli DNA, labeling the various nucleic acids, proteins/activities and directions for the DNA.


b. How does the replication fork in eukaryotes differ from that diagrammed above? (Are there differences in: topology, activities, molecules etc.?)

(10) 5. a. What are the "Two major principles of chaperone action...." ?


b. When and why are chaperonins needed? How do the structures of these proteins enables their operation?


(15) 6. Consider the reaction catalyzed by isoleucyl-tRNA synthetase.

a. Write-out, in detail and including structures, the chemical reaction(s) involved in joining the amino acid and tRNA. [ilu: CH3CH2CH(CH3)CH(NH3+)COO-]


b. Explain the extraordinary specificity of this enzyme.


(15) 7. a. Describe and compare the reactions catalyzed by the Types I and II Topoisomerases.


b. Are there any differences in the actions of these enzymes in prokaryotes and eukaryotes? Elaborate briefly.


c. Consider a small closed-circular piece of DNA with L = T = 100 initially. What will the values of the equation of its topology be after Topoisomerase I acts on it twice, and then Topoisomerase II acts on it once? Give a stepwise explanation.


(12) 8. Define and/or describe each of the following:

a. Genomic Library:


b. TATA box:


c. Spliceosome:


d. Replicon:

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Last modified 10 January 2002