Question

Inside a prokaryote, such as E. coli, an operon controls for the production of the amino acid tryptophan. What occurs in the cell in order to turn off the production of tryptophan?

Tryptophan binds with the promoter to block the DNA polymerase.
The operon binds to the RNA polymerase and releases the repressor.
Tryptophan binds with the repressor, allowing it to attach to the operator site, blocking RNA polymerase.
The RNA polymerase binds to the tryptophan, activating the repressor, blocking the promoter.

Answer 1

The operon binds to the RNA polymerase and releases the repressor.

Amino acids like tryptophan and tyrosine are used to produce neurotransmitters and other products. Hormones such a serotonin and melatonin are made products of tryptophan as well as norepinephrine and adrenalin.