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Lecture 14

Biology Lecture 14 Outcomes

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Western University
Biology 1002B
Tom Haffie

Lecture 14 **free ends are the 5’ end of the message A is the right answer ** promoters are double stranded structures that are interpreted by the cell as DNA, they are understood by RNA polymerase and DNA binding proteins. SD box works as mRNA Lactose Metabolism is regulated by the lac operon in E. Coli (prokaryotes)  Discovered that ecoli had ability to degrade lactose and grow on it  Has a side reaction: creates an isomer of lactose called Allolactose  Normally galactosidease activity is low, not zero Wild Type Phenotype is “inducible”  Some galactosidease is there all the time  If lactose is added, galactosidease activity increases  Lac operon is inducible by lactose Mutant Phenotypes lack inducibility  lacI- (I stands for inducibility minus)  these strains were not inducible, their galactosidease was constitutive  lacZ- don’t produce galactosidease at all  Lac y is a transporter for lactose, permeability gene  Lac I codes for repressor  lacZ and lacy share a promoter (fundamental component of operon, multiple genes controlled by one promoter)  Lac I has its own promoter  Represser binds to operator (DNA binding protein) but it can come off and on, so it’s the probability of the gene being expressed goes up and down  WHEN LACTOSE IS INTTRODUCE  Allo lactose bind the repressor and makes the repressor unable to bind to operator and shut down transcription so lots of galactosidease is made  IF LAC Z GENE IS BROKEN  No galactosidease is there to break down the lactose LAC operon  Lac a is an enzyme  Red part is the operator region  Blue part also part of operator  Green bits are two molecules of repressor protein- work together to bind onto the operator  They stabilize this crazy loo  This is not a hairpin o Hairpin is single strand bindi
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