Q) Outline the features of the lac operon in bacteria
Main points | |
Key idea: | What is an operon + components of the lac operon |
· An operon - a group of genes under control of a single promoter · For lac operon, set of structural genes, lacZ, lacY and lacA - codes for β-galactosidase, lactose permease and lactose transacetylase, respectively. 3 genes under control of a single promoter + operator + CAP binding site | |
Key idea: | Role of the structural genes |
· Genes code for enzymes involved in lactose metabolism of bacteria · β-galactosidase - breaks down lactose into glucose and galactose, also converts lactose to its isomer, allolactose. · Lactose permease - transports lactose into cells · Galactose transacetylase - unknown function is unclear | |
Key idea: | Role of the regulatory sequences (upstream of structural genes) |
· Promoter for RNA polymerase to bind, for transcription · Operator (b/w promoter and genes) for a repressor mol to bind to (in absence of lactose), to inhibit trancription · Catabolite activator protein (CAP) binding site (upstream of promoter) for cAMP-CAP complex to bind to (in the absence of glucose), to upregulate transcription | |
Comments: (i) Visualize the answer with the aid of labelled diagram + animation (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) (iv) The regulatory gene lac I coding for repressor which binds to the operator is not part of the lac operon (v) cAMP-CAP complex can simply be catabolite activator protein (CAP) | |
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