Monday, 10 December 2012

A Fusion Operon Question

What's a fusion operon?  Ask Dr. David Bird, an evil scientist who likes to test the understanding of his students regarding gene regulation by creating unholy and absurd mixtures of operons.  Well, that's overstating it, but it's a neat puzzle that is created by joining control structures from different operons together.

In this case, the CAP site and operator of a lac operon were fused to the trpL and structural genes of a trp operon.  Remember that the CAP site is for positive regulation, the lacO is bound by a repressor protein (it's not in this figure, but imagine it's there) in the absence of lactose.  The trpL is the leader sequence that allows attenuation (premature end of transcription unless tryptophan levels are really low - it does this by making a hairpin structure that results in rho-independent termination of transcription).

See if you can fill out this table using those cues.  Oh, and thanks go to Dr. Bird for his generously supplying me with this example problem (and Brittany for reminding me about this exercise)!

The solution: