Attenuation is a type of regulation that can control

Attenuation is the regulatory mechanism to control gene expression or transcription.  Attenuation was first observed in trp operon of E.Coli bacteria (commonly found at guts of warm blooded animal).  E.Coli bacteria need tryptophan which is a kind of amino acid. The bacteria can either take tryptophan from environment or itself synthesize by using bio synthetic enzymes. These bio synthetic enzymes are encoded by five genes located next to each other which we called as trp operon.

When tryptophan levels are high, then the transcription of trp operon is controlled. This process is called Attenuation. In this process the RNA polymerase is prematurely stopped during transcription of trp operon which results in formation of short mRNA. Due to premature control such mRNA doesn’t gets encoded with tryptophan biosynthesis enzymes.

Attenuation is carried out when tryptophan level is high, so as to prevent unnecessary production of biosynthetic enzymes which are needed to make tryptophan.