Question

1. A constitutive mutant is a strain that had a mutation in an operon leading to that strain continuously making protein (or continuous gene expression).  This operon is inducible in the wild type strain (no mutation) and therefore regulated.  What would be two possible explanations on how an inducible operon would become constitutive?  (hints: think about the different mechanisms of induction and then consider what would happen is these components had mutations)
2. With regard to the Lac operon, if a bacterium goes from a lactose-free medium to a medium containing lactose, how is the lactose able to enter the cell and eventually induce the operon?  
3. With regard to the Lac operon, if a bacterium goes from a lactose-free medium to a medium containing lactose, how is the lactose able to enter the cell and eventually induce the operon?  
4. Proportionally, how are [cAMP] and [glucose] related in bacterial cells? How is this relationship accomplished, and what enzyme is involved in the synthesis of cAMP?

Answer 1

Lac operon is a classical example of an inducible operon. When lactose is present in the cell it is converted into allolactose.Allolactose act as an inducer binding to repressor and preventing the repressor from binding to the operator. This allow the transcription and the constitution of the genes.

B. When lactose is the lac jeans are expressed because allolactose Binds to the lac operon repressor protein and keeps it from binding to the lac operator. Allolactose is an isomer of lactose and is formed in small amounts when lactose the bacteria.Allolactose binds to the the allosteric site of repressor protein causing a conformational change.As a result of this Change the repressor can no longer bind to the operator region and falls off.RNA polymerase can bind to the operator and the transcribe the lac genes.