Which is correct about operators and operons?
Select one: a. An operator is a repressor binding site; an operon consists of the gene cluster, promotor, and regulatory sequences. b. There is no difference; the terms are interchangeable (synonyms). c. An operator is a molecule that binds to an operon to facilitate binding of architectural regulators. d. An operon is a protein that binds to an operator sequence to repress transcription. e. An operon is a clustering of four or more operators.
The correct answer and explanation is:
The correct answer is: a. An operator is a repressor binding site; an operon consists of the gene cluster, promotor, and regulatory sequences.
An operon is a functional unit of genetic material found in prokaryotes. It consists of a group of genes that are transcribed together under the control of a single promoter. The genes in an operon usually encode proteins involved in a related biochemical pathway or process. The operon typically includes a promoter, which is the DNA sequence where RNA polymerase binds to initiate transcription, as well as additional regulatory sequences that control gene expression.
The operator is a specific DNA sequence located within or near the promoter region of an operon. It serves as a binding site for a repressor protein, which can block transcription when it binds to the operator. This mechanism is an essential part of gene regulation in bacterial cells. When a repressor protein binds to the operator, it prevents RNA polymerase from transcribing the genes in the operon, thereby stopping the production of the associated proteins.
The operon system allows the cell to coordinate the expression of multiple genes involved in a common function. For example, in the lac operon in E. coli, genes involved in the metabolism of lactose are transcribed together when lactose is present in the environment. The repressor protein binds to the operator when lactose is absent, inhibiting the transcription of these genes.
In summary, the operator functions as a repressor binding site, while the operon is the broader regulatory system that controls a set of genes. This system is crucial for the efficient regulation of gene expression in prokaryotic cells.