Operon concept allows prokaryotes to coordinate gene expression. An operon contains a group of genes that are transcribed together and regulate a metabolic pathway. The lac and trp operons demonstrate induction and repression of gene expression. The lac operon induces expression of lactose-metabolizing enzymes in response to lactose. In the presence of lactose, allolactose acts as an inducer to activate the lac operon. In contrast, the trp operon represses expression of tryptophan-synthesizing enzymes in the presence of tryptophan via a repressor protein. Operons allow prokaryotes to efficiently regulate metabolic pathways in response to environmental conditions.

1. OPERON CONCEPT
PRESENTED BY:-
dhiren bhoi
ROLL NO:-by1016
p.g first year
dhirenindia60@gmail.com

2. CONTENTS::-
* INTRODUCTION
* GENE
*GENE EXPRESSION
* NEED OF GENE REGULATION
* OPERON
* WORKING MECHANISM OF OPERON
* OPERON CONCEPT
*INDUCTION
* REPRESSION
*CONCLUSION
* REFERENCES

3. INTRODUCTION-
GENE-In molecular term gene commonly
defined as the entire nucleotide sequences that
is necessary for the synthesis of a fundamental
gene product.

4. HOW A GENE EXPRESS

5. Need of Gene Regulation-
Through the genes express to specify
a particular character regulation of
gene action is inevitable .
→If its not regulated ,the unwanted
biological products(RNA , protein)
produced unnecessarily that cause
the waste of energy & it may effects
other useful cellular activities .
So gene regulation is essential.

6. Gene organisation in prokaryotes “THE
OPERON”
Unlike eukaryotes in prokaryotes the genes are organised
into operon.

7. Operon- is a co-ordinated group of genes
which are all transcribed together &
regulate a metabolic pathway as a unit.

8. WORKING MECHANISIM OF AN OPERON

9. Jacob &Monod in 1961 while studying catabolism of
lactose in E.coli suggested that the action of most
genes is regulated at transcription level by
*Induction
&
*Repression.

10. INDUCTION
In induction synthesis of
enzyme takes place in
response to appearance
of specific substrate in
the medium.
The phenomenon of
induction can be
explained
by taking the example of
working of Lactose
operon.

11. Lactose operon-
Lac operon is a cluster of gene ,which controls
enzyme productions needed for catabolism of lactose.

12. Working of Lac- Operon
Beckwith(1967),Epstein &Beckwith (1968),Martin
(1969) have describe the operation of Lac operon in
E.coli.
→Working of Lac operon is
operated by two mechanism
(a)Negative control
(b)Positive control

13. WORKING IN ABSENCE OF LACTOSE

15. POSITIVE OR ALLOSTERIC REGULATION
OF LAC-OPERON
lactose, glucose{first} Lac & Glu{siml}

16. POSITIVE CONTROL-DNA-Activator protein
interaction causes switch off operon

17. LACTOSE ALLOLACTOSE
Not the lactose but allolactose is the actual
inducer

18. REPRESSION
In repression synthesis of enzyme halted in response
to appearance of specific substrate in the medium
It can be explained by taking working of tryptophan
Operon.
Tryptophan is an essential amino acid which is
required for synthesis of protein by bacterial cell.

19. Structure of Trp- operon
TRYPTOPHAN OPERON- Its a clusture of genes which
regulates enzymes production needed for
biosynthesis of tryptophan.

20. working in absence & presence of tryptophan
WORKING OF TRP-OPERON

21. CONCLUSION
As the gene expression
is needed to produce
a specific phenotype ,
regulation of gene action
is of same essence to
specify a given a phenotype
under a given circumstance.

22. References:
The Cell-Albert
Molecular Cell Biology-Harvery Lodish
The Cell-G.M.Cooper
Gene-IX-Lewin
Genetics-Verma & Agrawal
Genetics-Rastogi