BIO 302, Spring 2001

Review 2 - Microbial Genetics

Brief Answer Key

Answer 6 of the following 7 questions

  1. The anti-HIV drug ddI has the following structure:


    Explain its mode of action.

  3. Expression of the tryptophan operon is controlled by a repressor in a manner very similar to expression of the lactose operon. The tryptophan operon also is regulated via a process known as attenuation. Describe this process.
  4. Compare and contrast transformation and generalized transduction.
  5. A) For the following lac operon partial diploids, list which genes will be expressed in the presence and absence of lactose. NOTE: A (-) next to a gene indicates that a mutation exists in that gene that precludes expression of that particular gene. Genes preceding the slash exist on a plasmid. Genes following the slash exist on the chromosome.

  6. 1. I-O+Z+Y+A+ / I+O+Z+Y+A+

    2. I-O+Z-Y+A+ / I-O+Z+Y-A+

    3. I+OcZ+Y-A+ / I-O+Z-Y+A+

    4. I-OcZ-Y-A+ / I+O+Z+Y+A+

    B) Mutations in the lacI gene have been identified that abolish the ability of the repressor (I) to bind to lactose (all other functions of the repressor remain unchanged). Briefly describe the effects of these mutations.

  7. Eukaryotic mRNAs are monocistronic. Prokaryotic mRNAs, however, may be polycistronic. Why?
  8. Molecular biologists often comment that positive sense, single stranded RNA viruses possess infectious RNA. What is meant by this statement? Why is the same comment not true for negative sense, single stranded RNA viruses?
  9. The local chapter of Fish R Us has hired you as a consultant. They are trying to produce large amounts of fish growth factor to dump into Lake Norman and, hopefully, increase the size of the bass in the lake. They have cloned the complete fish growth factor gene, including all its regulatory regions, into a bacterial plasmid and transformed E. coli with this plasmid. These bacteria, though, are not producing fish growth factor. What are your recommendations to them? Explain why you made these recommendations.