how does lac operon operate in the prokaryotes
Answers
Explanation:
Key points about lac operon
- Found in prokaryotes not eukaryotes
- Given by
Biochemist : Jacque Monad
Geneticist : Francis Jacob
- Lactose is the inducer which means presence or absence of lactose decides whether operon works or not
- Consist of 5 genes
1. Regulator (i) : Synthesises inhibtor molecule continuously (constitutively)
2. Promoter (p)
3. Operator (o) : Binding of RNA polymerase. Inhibitor binds here when lactose is absent
4. Structural genes : They synthesise
z gene - Beta galactosidase - Metabolism (Hydrolysis) of lactose
y gene - Permease - Enhances permeability of beta galactosidase into the cell
a gene - Transacetylase
If lactose is present, it binds to inhibitor. So RNA polymerase can move freely and structural genes can synthesize the enzymes. This is switch on condition
If lactose is absent, it does not binds to inhibitor. So inhibitor binds to operator and RNA polymerase cannot move freely and structural genes cannot synthesize the enzymes. This is switch off condition.
Note : Lac operon is under negative regulation
To better your understanding, refer Fig 6.14 from Class XII Biology NCERT page 117
Hope it helps