Question

Discuss the genetic control of enzyme activity with the help of operon model.

Answer 1

Control of enzyme activity or enzyme secretion is needed in order to control the normal body growth and metabolism. One of the mechanism that is used to control gene expression and thus enzyme activity is by Operon Model. 

Operon is regulatory gene that is consists of
- Regulator Gene - responsible for repressor protein expression
- Promotor - RNS polymerase attachment site
- Operator - Repressor biding site
- Structural gene - Enzyme coding sequence of gene

Gene expression and thus enzyme activity is controlled either by Repressors or Activators. 

Repressors control the activity by blocking mRNA transcription. Repressors bind to a portion of DNA also known as operator which is downstream of promoter. This binding prevents that RNA polymerase binding and thus prevents further activity. Example is trp operon. 

Activators control the activity by activating genes which has a promoter which disables the RNA polymerase binding. In this case, promoter is situated close to activator binding site. In normal condition, this is allosteric protein to which RNA polymerase can not bind. Thus preventing gene expression. 

Attached is the textbook image of trp operon for your reference. 

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