BIO220 Lec 2

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Published on 5 Oct 2011
School
UTSG
Department
Biology
Course
BIO230H1
Regulation of genome expression
Screen clipping taken: 9/15/2011, 1:12 PM
Responses to extracellular stimuli
Defining cell types in multicellular organisms
Regulation of gene expression crucial for
Recall DNA is transcribed into RNA by enzyme RNA polymerase
Screen clipping taken: 9/15/2011, 1:13 PM
Many different types of RNA
Lecture 2
Thursday, September 15, 2011
1:10 PM
BIO230 Page 1
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Document Summary

Recall dna is transcribed into rna by enzyme rna polymerase. In eukaryotes , rna polymerase ii requires general transcription factors (tb: tb. Gene regulatory proteins (aka transcription factor) in both prokaryotes and eukaryotes. Bind to regulatory regions of dna (aka cis elements) In prokaryotes multiple genes can be transcribed into a single rna molecular. Only on if levels of tryptophan are low. Repressor must bind to two molecules of trp in order to bind to dna. Tryptophan repressor contains helix-turn-helix dna binding motif (most common dna0binding motif) Helix-turn-helix binds to major groove of dna helix. Fits in major groove: coli lac operon. 3 genes required for transport of lactose into cell. Enables use of lactose in absence of glucose. When lactose levels are low, lac repressor is bound to operator. Increase lactose, increase allolactose levels beta-galactosidase changes lactose to allolactose. If glucose is present, cap is not found, therefore operon not on.

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