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Lecture 14

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Biology 1002B
Tom Haffie

Lecture 14: Eukaryotic Gene Expression  Where is your gold today? o Make pictures of genes showing he relative location of signals o Make a chart of signals and how they are understand o Make a list of RNA functions o Make a diagram of gene expression that highlights complementary base pairing o Make a chart comparing prokaryotes and eukaryotes  Eukaryotes can keep the ribosomes away from the mRNA just been translated from the nucleus because of the nuclear membrane  Clicker question o The synthesis and function of a typical tRNA molecule requires complimentary base- pairing with:  Itself  yes  DNA  In transcription, it base-pairs  Other RNA  yes  Does not pair with amino acids, cannot pair, not bases  Operons bring several genes the control of one promoter  PHET lac operon simulation  Clicker Question o How many stop codons (in DNA) are there in this picture?  4 stop codons in the picture  Every protein has a stop codon i.e. Lac I, Lac X, Lac Y, Lac Z  Keeping mRNA away from the ribosomes are very important o Prokaryotes cannot do that  Eukaryotic regulation o Transcriptional regulation  Regulation of transcription initiation o Posttranscriptional regulation o Translational regulation o Posttranslational regulation  Nuclear gene structure is more complicated than in organelles o TATA box o Promoter proximal region, area where proteins bind (protein binding sites) o How do eukaryotes stop transcription? o Enhancers can be far away o Genes do not have to have introns, eukaryotic often have introns, some have hundreds of introns  RNA polymerase II does not bind to “naked” promoters o More than one polymerase in eukaryotes o Polymerase II transcribes protein genes (PCG)  Only find promoters attractive when they have protein on the gene o They need the TATA promoter  Protein binds to the TATA promoter  Transcription factors regulate efficiency of polymerase binding  Helix-turn-Helix DNA binding motif o Proteins are not making covalent bonds with DNA o Just electro-static o Lac repressor is a helix turn helix  Zinc Finger DNA binding motif binds the major groove o Series of amino acids can associate with zinc cofactors o Protein motifs o DNA binding protein motifs  Leucine zippers hold two monomeric DNA binding proteins together o Holding the dimers together, zips one dimmer onto another o To some kind of DNA binding protein  Promoters and enhancers o DNA can loop and bend o Promoters are position dependent, move it far away from the gene, it no longer works o Promoters are direction dependent o Enhancers are less position dependent, it’ll work mostly everywhere  They bind to activators and trap the complex and maximize transcription o There are silencers, which makes it all go away o There are activators near the promoter proximal region and some activator on the enhancer, and the enhancer will bond with co-activator and bends to and attach on to the promoter  i.e. making a sandwich  enhancer makes the promoter more attractive  enhancer holds the co-activator in place to make promoter more attractive  Unique combinations of activators control specific genes o Express different activators will produce different genes coding for different proteins in different tissues o Regulating their enhancers can regulate which genes to express by controlling the activator it has  Cells tend to invest heavily in regulation of transcription  Polyadenylation signal o
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