Lac operon in E. coli is a classic example of Gene expression occurring at transcription
Step-by-step explanation:
A lac operon is a type of bacterial operon which is a cluster of co-regulated genes. In order to adapt to environmental changes, the related genes are grouped in an operon.
When lactose is absent, the E. coli bacteria group related genes and produce enzymes (lacZ, lacY, lacA) which help in lactose metabolism to encode the unexpressed lactose.
Structural genes that specifically code for amino acids are called gene expressions. This takes place at two levels – transcription and translation.
Lac operon operation involves promoter, operator, CAP-binding site sequences. The gene group binds with the promoter and is transcribed as a single mRNA.