PLEASE HELP The tryptophan operon in some bacteria is a repressible operon. Which of the following statements correctly describes this operon?

It is activated only when glucose is present in the growth medium.
It is deactivated whenever tryptophan is added to the growth medium.
It is activated only when tryptophan is present in the growth medium.
It is permanently active.

What is the difference between a meteoroid and a meteor?

The hershey and chase experiments involved the preparation of two different types of radioactively labeled phage. which of the following best explains why two preparations were required? a. the bacteriophage used in the experiments was a t2 phage. b. it was necessary that each of the two phage components, dna and protein, be identifiable upon recovery at the end of the experiment. c. each scientist had his own method for labeling phage, so each conducted the same experiment using a different isotope. d. establishing the identity of the genetic material required observation of two phage generations.

Hormones that bind to plasma proteins