Write short note on lac operon
 

Vedclass pdf generator app on play store
Vedclass iOS app on app store

Francois Jacob and Jacque Monod in $1961$ were the first ones to propose the concept of transcriptionally regulated by a common promoter and regular genes.

Such an arrangement is referred as an operon eg. lac (lactose) operon, trp (tryptophan) operon, arn (arabinose) operon, his (histidine) operon and val (valine) operon.

Structure of lac operon : The lac operon consists of one regulatory gene (the $i$ gene-here the term $i$ does not refer to inducer, rather it is derived from the word inhibitor) and three structural genes ($z$,$y$and $a$).

The $i$ gene codes for the repressor of the lac operon.

The $z$ gene codes for beta-galactosidase ($\beta-gal$) which is primarily responsible for the hydrolysis of the disaccharide, lactose into its monomeric units galactose and glucose.

The $y$ gene codes for permease which increases permeability of the cell to $\beta$-galactosides.

The $a$ gene encodes a transacetylase.

Hence all the three gene products in lac operon are required for metabolism of lactose.

In most other operons as well the genes present in the operon are needed together to function in the same or related metabolic pathway.

Lactose is the substrate for the enzyme beta-galactosidase and it regulates switching on and off of the operon.

Hence, it is termed as inducer.

968-s42

Similar Questions

$A$ : Lac operon exerts negative control only.
$R$ : The operator is occupied by aporepressor during regulation

In an Ecolistrain $i$ gene gets mutated and its product can not bind the inducer molecule. If growth medium is provided with lactose, what will be the outcome?

  • [NEET 2022]

Lac operon is

Jacob and Monad studied lactose metabolism in E. coli and proposed operon concept, which is applicable for

  • [AIPMT 2002]

Terminator gene