Question

Explain the following term in connection with the concept of the lac operon in E.coli:

Polycistron

Answer 1

In the lac operon of E. coli, a polycistron (or polycistronic mRNA) refers to a single messenger RNA molecule that carries the genetic information to encode multiple different proteins. Unlike humans, who typically have one gene per mRNA, bacteria like E. coli group related genes together under one control system. When the lac operon is switched on, RNA polymerase transcribes lacZ, lacY, and lacA into one continuous mRNA strand. This allows the cell to produce all three enzymes β-galactosidase, permease, and transacetylase simultaneously and in equal amounts, ensuring the entire metabolic pathway for lactose is activated at once.