Question

How does the Trp repressor prevents RNA polymerase from initiating transcription?

by blocking the ribosome binding site

by forming a loop in the operator that restricts the passage of the polymerase

by binding to the polymerase to inhibit its catalytic activity

by physically blocking the DNA binding site of RNA polymerase

Answer 1

ANSWER: by physically blocking the DNA binding site of RNA polymerase.

Trp repressor or typtophan repressor is useful for amino acid metabolism.

The main function of Trp repressor is to repress the Trp operon when trytophan levels are high.

On the contrary, when trytophan levels in the cell are less, Trp repressor becomes inactive.

Thus, to switch of/ repress, the repressor identifies the stretch of DNA. Then it physically binds to the DNA binding site of the RNA polymerase and prevents trancription.

RNA polymerase is the enzyme responsible for synthesizing RNA sequence from that of a DNA sequence. This happens in the process of transcription.

Hence, if DNA binding site of RNA polymerase is blocked physically by the Trp repressor then it prevents trancription from taking place.