OPERON CONCEPTPRESENTED BY:-

dhiren bhoiROLL NO:-by1016

p.g first year

dhirenindia60@gmail.com DEPARTMENT OF BOTANY

BERHAMPUR UNIVERSITY

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

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

HOW A GENE EXPRESS

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.

Gene organisation in prokaryotes “THE OPERON”

Unlike eukaryotes in prokaryotes the genes are organised into operon.

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

WORKING MECHANISIM OF AN OPERON

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.

INDUCTIONIn 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.

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

Working of Lac- OperonBeckwith(1967),Epstein &Beckwith (1968),Martin (1969) have describe the operation of Lac operon in E.coli.

→Working of Lac operon isoperated by two mechanism

(a)Negative control(b)Positive control

WORKING IN ABSENCE OF LACTOSE

NEGATIVE CONTROL-DNA-Protein interaction cause switch off gene expression

POSITIVE OR ALLOSTERIC REGULATION OF LAC-OPERON

lactose, glucose{first} Lac & Glu{siml}

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

LACTOSE ALLOLACTOSE

Not the lactose but allolactose is the actual inducer

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.

Structure of Trp- operon

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

working in absence & presence of tryptophan

WORKING OF TRP-OPERON

CONCLUSIONAs 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.

References:The Cell-AlbertMolecular Cell Biology-Harvery LodishThe Cell-G.M.CooperGene-IX-LewinGenetics-Verma & AgrawalGenetics-Rastogi