When tryptophan is abundant inside an E. coli cell, two tryptophan molecules bind the trp repressor protein. What does the repressor then do, and what is the overall effect on transcription?

1. When tryptophan is present in the cell, two tryptophan molecules bind to the trp repressor protein. 2. This binding changes the repressor's shape so that it can bind to the trp operator sequence. 3. Binding of the tryptophan-repressor complex at the operator physically prevents RNA polymerase from binding and transcribing the downstream genes. 4. Because the repressor actively binds the operator to keep genes off, the trp operon is described as negatively regulated. 5. The option describing the repressor detaching entirely is the opposite of what happens when tryptophan is present, since binding is what turns transcription off. 6. Prokaryotic cells lack a nucleus, so a mechanism that drags RNA polymerase into a nucleus does not apply here. 7. The repressor does not convert into an activator; it remains a repressor whose binding blocks transcription. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 16 "Gene Expression", section The trp Operon: A Repressor Operon_