lac operon in bacteria - ✔✔- lac operon is a regulated promoter
- it is regulated by catabolite activator proteins (CAP) that bind next to a
promoter to recruit RNA polymerase
- it is repressed by the lac repressor which binds downstream of the
transcription initiation site
lac operon (- lactose, + glucose) - ✔✔- glucose is the preferred source of
energy so when it is present, there are low levels of cyclic AMP (cAMP)
and the lac repressor is bound downstream of the promoter site
- this inhibits the binding of the polymerase
lac operon (+ lactose, +glucose) - ✔✔- the lac repressor is activated in
the presence of lactose
- the 4 binding sites of the lac repressor are each bound by lactose
- this releases the lac repressor from blocking the transcriptional initiation
site
- transcriptional rate is low because there is still a presence of glucose and
therefore, the cAMP isn't bound
- glucose is still being metabolized
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