The document describes the lac operon system, which was the first operon described in 1961 and controls the catabolism of lactose in prokaryotes. The lac operon has 5 structural units - a promoter, operator, three structural genes (LacZ, LacY, LacA) that encode enzymes for lactose breakdown, CAP binding sites, and a regulatory gene. When lactose is absent, a repressor protein binds to the operator, preventing transcription of the structural genes. When lactose is present, it binds to the repressor and causes a conformational change that releases it from the operator, allowing transcription and the breakdown of lactose.

1. LAC OPERON SYSTEM

2. INTRODUCTION
 Operon can be defined as the
cluster of genes located together
on the chromosome and
transcribe together.
 Control- biochemical process.
 Found- Prokaryotes.
 History- 1st described in 1961 by
Francois Jacob and Jaques
Monod, of the Pasture Institute
of Paris.
 Lac operon involved- catabolism
of lactose.
 Lactose made up- Glucose and
Galactose.

3. LAC OPERON MODEL
5 Structural units-
1.Promoter-
2.Operater-
3. Structural gene -
Lac z, Lac y, Lac a
4. CAP binding
sites-
5.Regulatory gene-

4. THE REGULATION OF THE LAC OPERON
When lactose is absent- When lactose is present-

5. THE REGULATION OF THE LAC OPERON
When both glucose and
lactose are present
When glucose is absent
and lactose is present

6. THANK YOU