Sample questions for exam 2:

1. Upon completing graduate school you find employment with NASA where you are leading a team of scientists that have discovered living organisms on a moon of Jupiter. Amazingly these organisms have a DNA genome where genes are transcribed into mRNA and translated into proteins. However there are 26 amino acids in these organisms and all are different than those found in earthly creatures, what experiments would you do to solve the genetic code in these extraterrestrial beasts?

2. Discuss the events that occur when during translation (protein synthesis) the ribosome comes to a stop codon. Discuss what happens to the ribosome, tRNA, mRNA, and polypeptide chain.

3. You are working with a strain of bacteria that is cys^-. Design an experiment that will allow you to transfer the cys⁺ gene to the auxotrophic strain from a prototrophic strain. Unfortunately the cys^- auxotrophic strain you are working with is not able to become competent.

4. Does protein synthesis require energy? If it does, give the sources for the energy required to synthesize new proteins in the cell.

5. How does a bacteria that is F⁺ differ from a strain that is Hfr. How do these strains differ in their ability to donate chromosomal genes to an F^- cell?

6. Using the universal genetic code (table in your text on p. 267) give the amino acids which are specified for by the following codons:
UCU
CUC
AUG
CUU
GAC
Which of the above is the initiation codon for translation?

7. Discuss how the presence of glucose affects the level of transcription of the lac operon. Describe the expression of the lac operon in the presence and absence of glucose and show the protein that regulates this effect. Include a discussion of how the protein mediates this effect.