Well, if we have a low amount of tryptophan inside the cell then our inactive repressive protein will remain inactive because there isn't enough tryptophan to actually bind onto the allosteric side of this inactive repressive protein to activate it. So usually what happens is this gene is expressed to produce the repressor mRNA and then that mRNA is used to form the inactive repressor protein. And because we don't have enough we don't have a lot of tryptophan in our cell. The tryptophan will not bind to this protein. It will not activate it and so nothing will bind to the operator section and nothing will block the transcription of these genes. And what that means is the RNA polymerase will easily bind onto the promoter section, the blue section.