Topic Genetics of Bacteria Essay - Main Points!

Q) Explain the effect of different level of lactose on the activation of the Lac operon

Main points
Key idea:	Components of Lac operon
·Structural genes - lacZ, lacY and lacA genes; codes for β-galactosidase, lactose permease & lactose transacetylase, respectively ·Ref to metabolism of lactose ·Ref to genes organized to be under control of a single promoter & operator (i.e. lac operon) whose expression are coordinately regulated at diff level of lactose in the envt of prokaryotic cell
Key idea:	Effect of low level of lactose in the environment
·Some lactose transported into cells by low level of lactose permease present ·Lactose converted to allolactose by low level of β-galactosidase present ·Allolactose inducer binds to repressor, changes its specific conformation ·Repressor unable to bind to operator site b/w promoter & genes ·RNA polymerase can bind to promoter, transcribe genes, result: synthesis of inducible enzymes
Key idea:	Effect of higher level of lactose in the environment
·When level of lactose increases, more repressor unable to bind to operator site ·Catabolite activator protein (CAP) binding site upstream of promoter bound to catabolite activator protein ·Result: a higher expression of lac genes; more lactose metabolized, greater amount of glucose as respiratory substrates for syn of ATP via cellular respiration
Key idea:	Effect of glucose on the activation of the lac operon
·[Glucose present] - lac operon switched off ·Reason: glucose prevents syn of cAMP required for active form of CAP. ·Hence, CAP binding site not bound by CAP ·Operon is switched off due to glucose repression ·The lac operon to respond appropriately to varying conc of lactose ·When glucose is available, ref to operon sys to help direct limited resources & energy of bacteria toward other important metabolic activities
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min)