(1) operator (2) promoter molecules that stimulate gene expression (3) operon site where RNA polymerase binds site where a repressor can bind sets of genes that code for proteins with related functions

Below is an explanation of the three terms and the corresponding definitions: 1. Operator  • Definition: The operator is the site where a repressor (or other regulatory proteins) can bind. When a repressor binds to the operator, it typically blocks the RNA polymerase from transcribing the downstream genes. 2. Promoter  • Definition: The promoter is the site where RNA polymerase binds to initiate transcription. It is a region of DNA that signals the start of a gene. 3. Operon  • Definition: An operon is a set of genes that code for proteins with related functions and are transcribed together from a single promoter. Often, an operon includes a promoter, an operator, and one or more structural genes.  • Also Related: Molecules that stimulate gene expression (generally known as activators) are factors that help increase the rate of transcription, often by binding to specific DNA sequences near the promoter. In summary: – The operator is the regulatory DNA segment where repressors bind. – The promoter is the DNA sequence where RNA polymerase attaches to begin transcription. – The operon is a cluster of genes transcribed as a single unit whose proteins are related in function.