The trp operon: Bacterial cells can take up the aminoacid tryptophan from their surroundings, or, if the external supplyis insufficient, they can synthesize tryptophan from smallmolecules in the cell. Â
When external supplies of tryptophan are plentiful, thecells suppress transcription of the trp operon, which encodes thetryptophan biosynthetic enzymes. When external supplies oftryptophan are not plentiful, the cells express the trpoperon.
The trp operon repressor protein inhibits transcriptionof the genes in the trp operon. Upon binding tryptophan, thetryptophan repressor binds to a site in the promoter of the operonand represses transcription.
A. (2 pts) Why is tryptophan-dependent binding to theoperon a useful property for the tryptophan repressor?
B. (4 pts) How would regulation of transcription oftryptophan biosynthetic enzymes be affected in cells that express amutant form of the tryptophan repressor that (i) cannot bind to theDNA or (ii) bind to DNA even when no tryptophan is bound to it?Also address how tryptophan synthesis would be affected and howthat would affect the cell. Please bullet point your response (i)and (ii) for each mutant for ease of grading.
