How gene expression is regulated? - Module 4 Reading / Watching

Bacteria such as E. coli need amino acids  like tryptophan to survive, which they can ingest from the environment.

 E. coli can also synthesize tryptophan using enzymes that are encoded by five genes in the tryptophan (trp) operon .

If tryptophan is available in the environment, then there is no necessity for   E. coli does  to synthesize it and the trp operon is switched off. However, when tryptophan availability is low,  the operon is turned on, transcription is initiated, the genes are expressed, and tryptophan is synthesized.

Like lac operon , trp operon also consists of structural genes and regulatory genes

The regulatory genes include

P/O genes :  Promoter sequence and the operator sequence which is found in the promoter region.

trp L : Leader sequence : attenuator (A) sequence is found in the leader

The structural genes are

The trp operon is a repressible systems because  the binding of the effector molecule to the repressor greatly increases the affinity of repressor for the operator . The repressor binds to the operator  and stops transcription. Thus if tryptophan  (effector) is  available in the medium   the repressors binds at the operator and repress the trp operon.