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Some gene regulation is positive

Some gene regulation is positive - ,E. Thee

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Some gene regulation is positive. Positive  gene control occurs when a protein molecule interacts directly with the genome to  switch transcription on. The  lac  operon is an example of positive gene regulation. When glucose and lactose are both present,  E. coli  preferentially uses glucose. The enzymes for glucose breakdown in glycolysis are always present in the cell. Only when lactose is present  and  glucose is in short supply does  E. coli  use lactose as an  energy source and synthesize the enzymes for lactose breakdown. When glucose levels are low,  cyclic AMP (cAMP)  accumulates in the cell. The regulatory protein  catabolite activator protein (CAP)  is an  activator  of transcription. When cAMP is abundant, it binds to CAP, and the regulatory protein assumes its active shape  and can bind to a specific site at the upstream end of the  lac  promoter.
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