Your lab is studying gene expression of the tryptophan opero

Your lab is studying gene expression of the tryptophan operon in the bacterium E. coli. In order to facilitate this study, you have cloned the Trp-operon, excised the five coding genes (TrpA, B, C, D, and E), and replaced them with a copy of the reporter gene GFP (green fluorescent protein). The resulting recombinant DNA was inserted into an F plasmid, and used to transform a number of different strains of E. coli. For each of the scenarios listed below, predict what the bacterial colonies would look like, and explain why you would obtain these results. a. A \"wild type\" strain of E. coli, transformed by the F Trp/GFP reporter plasmid, is plated out on a selective medium lacking tryptophan. b. A \"wild type\" strain of E. coli, transformed by the F Trp/GFP reporter plasmid, is plated out on tryptic soy medium. A trpR^- mutant strain of E. coli, transformed by the F Trp/GFP reporter plasmid, is plated out on tryptic soy medium.

Solution

Tryptophan is essential amino acid which is required by ecoli. It\'s synthesis is regulated by five genes located next to each other what is called as trp operon which regulates it\'s Synthesis. When tryptophan availability is low operon is switched on,genes are transcribed, enzymes are made and tryptophan is produced.

Answer a: when plated on tryptophan lackeng media operon is switched on and tryptophan is synthesized

AnswerB: In presence of tryptophan operen is switched off,transcription and hence synthesis stops.

Answer C: In mutant strain when GFP binds to DNA of operator it keeps the operon away from being transcribed by getting in the way of RNA POLYMERASE and hence stops trpytophan synthesis.