WHAT THE PROGRAM IS ABOUT::

        Many enzymes, i.e. proteins, involved in the catabolic degradation of their substrates, are not synthesised unless the cells are in a medium containing the substrates for those enzymes. That means,there are known cases where gene expression is inducible.The model that has been simulated here exemplifies this phenomenon.
When the bacterium Esherichia coli grows in a medium containing, say, glycerol as  the carbon source,it synthesises only small amount of the enzyme required for the degradation of lactose. If, however, lactose is added to the medium,  the cells will rapidly  start  to  synthesise  carrier molecules (called permease) to transport lactose into the cell  and  enzymes  β- galactosidase (and acetylase) to hydrolyses lactose into glucose and galactose.