Janka
Forum Senior
Topics: 28
Posts: 146
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1) lac operon
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| Del26
Forum Newbie
Topics: 1
Posts: 2
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thanks Janka, now what is the name given to the region where the enzymes of the lac operon proceed. i.e the region which is responsible for the regulation of the lactose metabolic genes
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| Janka
Forum Senior
Topics: 28
Posts: 146
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lac operon has 3 (rather 4) structural genes:
1. Z gene -> beta-galactosidase
2. Y gene -> some lactose transporter
3. A gene -> some enzyme with unknown function
4. i gene -> part of lac op. but located far away from it, encodes lac repressor, constitutively expressed. it's far upstream from the promoter.
now the regulatory part:
- lac repressor binds to the operator (a DNA sequence downstream of the promoter and upstream of the Z gene)
- cAMP dependent activator protein = CAP binds to the CAP site (a DNA sequence upstream of the promoter)
and finally the sugars:
- lactose prevents the repressor from binding the operator -> induces gene expression of the structural genes needed for lactose metabolism (see above)
- glucose lowers cAMP level -> CAP can't bind to CAP site -> represses gene expression
to summarize:
high gene expression only when lactose high and glucose low.
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| Jigna
Forum Newbie
Topics: 2
Posts: 3
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thanks again.
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