When I was 15 years old I got my first job at Burger King. This was the summer between my Sophomore and Junior year of high school. Literally the second day on the job, a woman and her three kids pulled up in the drive through. Still being naive and thinking everyone was a good person, I happily greeted them.
2 years ago. The difference between positive and negative control over transcription is that positive control promotes transcription and increases the frequency of initiation of transcription while negative control of transcription prevents the initiation of transcription and acts a repressor when glucose is present.
The trp operon is regulated through negative control only. When tryptophan is present, the operon genes are not transcribed. The lac operon is regulated through both negative control and positive control. Negative control: When lactose is absent, the repressor protein is active, and transcription is turned off.