Final answer:
A mutation in the trp operon that prevents the repressor from binding would lead to constitutive expression of the operon. The correct answer is option b).
Step-by-step explanation:
If the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding, the operon would be constitutively expressed. Normally, the trp operon is a repressible system where the repressor protein binding is dependent on the presence of tryptophan.
When tryptophan is absent, the repressor does not bind to the operator, allowing the genes to be transcribed and tryptophan to be synthesized. However, with a mutation impeding the repressor’s ability to bind, the operon would continuously express the genes required for tryptophan synthesis, regardless of the tryptophan levels in the cell.
This unregulated expression could lead to an excess of tryptophan and an inefficient use of cellular resources. n the absence of the repressor protein binding, the RNA polymerase would have unrestricted access to the promoter, leading to continuous transcription.