KIN217 Lecture Notes - Lecture 20: Oden

4. When a scientist makes a genetically modified bacterium as a tool for other experiments, there is always a fear that it might get out of the lab and wreck the environment. So there has been an interest in developing a “kill switch,” by which the scientist could ensure the bacterium only grows in the lab. Recently, one way to do this has been developed, wherein an artificial amino acid (that is not found in nature) is required for bacterial growth. To make this work, the artificial amino acid (call it ‘amacX’) must be encoded by the bacterial mRNA, recognized by a tRNA, and must be provided as a growth factor in laboratory media.

A. Look at the Genetic Code. How would you decide which of the codons you should use to represent amacX? (There may be more than one possible choice, so focus more on general principles than on a specific codon.) Are there any codons that you couldn’t use for this purpose? Why couldn’t you use them?

B. The gene for which enzyme would have to be mutated to make this work? Specifically, what mutation would need to be introduced to this enzyme? [Make a sketch as part of your answer.]

C. Let’s say this organism escapes into a natural environment where there is no amacX. Make another sketch showing what a Ribosome from this bacterium would look like when it encounters an amacX codon during translation. What would happen to this Ribosome?