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.
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