Faculty of Agriculture RUSL

1. Lac operon
D.M.S.K. Dissanayaka

2. What is operon?
• In genetics,an operon is a functioning unit of
genomic DNA containing a cluster of genes
under the control of a single promoter.

3. What is Lac operon?
• lac operon (lactose operon) is an operon
required for the transport and metabolism of
lactose in Escherichia coli and many other
enteric bacteria.

4. • Glucose is the preferred carbon source for most
bacteria.
• The lac operon allows for the effective digestion
of lactose when glucose is not available.
• Gene regulation of the lac operon was the first
genetic regulatory mechanism to be understood
clearly

5. Component of Lac operon
1. Promoter
2. Repressor
3. Operator (controlling site)
4. Coding sequences
lacZ, lacY, and lacA.

6. Lac-operon function
• when only glucose is present

7. • When only lactose is present the model works
as follows

8. • -galactosidase (lacZ)
• Breaks lactose into glucose + galactose.
• Lactose permease (lacY)
• Transports lactose across cytoplasmic membrane.
• Transacetylase (lacA)
• transfers an acetyl group from acetyl-CoA to -galactosides.

9. After the Lactose concentration reduce

10. • Finally from this lac operone control the
enzyme production & prevent the wastage of
energy.