the lac operon - mercer county community college - mccc - west

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1 The Lac Operon 1961, Jacob and Monod E. coli and other bacteria Bacterial Genes Many genes constitutively expressed “housekeeping” genes Other genes are more regulated Can be turned on, or off depending on cell needs

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Post on 11-Feb-2022

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No Slide TitleE. coli and other bacteria
Bacterial Genes
Can be turned on, or off depending on cell needs
Operon
1 promoter for a number of genes
Polycistronic mRNA
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BUT, if lactose is used instead:
convert lactose to glucose and galactose
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coordinate gene expression
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Lac Z gene encodes betagalactosidase
b-gal
Add lactose 3,000 molecules of bgal
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So…………………..
inducer
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C. operator = must be unbound for P to be
“open”
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Lac Y gene encodes permease that transports lactose into cell
Lac A encodes a transacetylase
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Is lactose PRESENT or ABSENT?
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In trans?
Its normally repressed! = OFF
Because lactose is absent
When lactose is present
conformational change
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5. Cell metabolizes lactose
Binds repressor protein causing a conformational change

No lactose:
Mutant Mutant Phenotype
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lactose?
In presence of lactose?
of lactose?
In presence of lactose?
F’ I+ Inducible?
I+P+O+Z- Y+A+
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Inducible?
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cannot move