Question

Distinguish between structural gene, regulatory gene and operator gene.

Answer 1

Structure of the operon: Each operon is a unit of gene expression and regulation and consists of one or more structural genes and an adjacent operator gene that controls the transcriptional activity of the structural gene.

1. The structural gene codes for proteins, rRNA, and tRNA required by the cell.
2. Promoters are the signal sequences in DNA that initiate RNA synthesis. RNA polymerase binds to the promoter prior to the initiation of transcription.
3. The operators are present between the promoters and structural genes. The repressor protein binds to the operator region of the operon.

Answer 2

Feature	Structural Gene	Regulatory Gene	Operator Gene
Primary Role	The “Worker”: Codes for actual enzymes or functional proteins.	The “Manager”: Controls the expression of other genes.	The “Switch”: Acts as a physical binding site for control.
Product	Produces functional proteins (e.g., β-galactosidase, permease).	Produces a regulatory protein (e.g., Repressor or Activator).	Does not produce a protein; it is a DNA sequence.
Location	Usually located downstream, at the end of the operon.	Often located upstream, away from the structural genes.	Located between the promoter and the structural genes.
Function	Performs the metabolic or structural work of the cell.	“Senses” the environment and produces the signal to turn the operon on/off.	Receives the repressor protein to block or allow RNA polymerase.