Final answer:
When tryptophan is abundant, it binds to the trp repressor, enabling the complex to bind to the trp operator and inhibit transcription, preventing the synthesis of more tryptophan.
Step-by-step explanation:
When tryptophan associates with the trp repressor, the resulting complex can bind to the trp operator and inhibit transcription. This process is a classic example of negative feedback in gene regulation. The trp operator is a DNA sequence located between the promoter and the first coding gene of the trp operon, which contains the DNA code for the repressor protein to bind. When tryptophan levels are high inside the cell, two tryptophan molecules bind to the trp repressor, altering its conformation so that it can attach to the trp operator. This binding prevents RNA polymerase from attaching to the promoter, thus blocking transcription of the genes needed for tryptophan synthesis. As a result, when the cell contains sufficient amounts of tryptophan, it prevents the synthesis of more, efficiently regulating the production of this amino acid based on its cellular concentration.