Question
Describe Lac ‘Operon’.
✓
Answer
Lac operon consists of the following components:
(1) Regulator gene:
- Regulator gene precedes the promoter gene.
- It may not be present immediately adjacent to operator gene.
- Regulator gene codes for a repressor protein which binds with operator gene and represses (stops) its action.
(2) Promoter gene:
- It precedes the operator gene.
- It is present adjacent to operator gene.
- RNA Polymerase enzyme binds at promoter site.
- Promoter gene base sequence determines which strand of DNA acts a template.
(3) Operator gene:
- It precedes the structural genes.
- When operator gene is turned on by an inducer, the structural genes get transcribed to form m-RNA.
(4) Structural gene:
- There are 3 structural genes in the sequence lac-Z, lac-Y and lac-A.
- Enzymes produced are β-galactosidase, β-galactoside permease and transacetylase respectively.
Inducer Allolactose acts as an inducer. It inactivates the repressor by binding with it.
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