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23 Cards in this Set
- Front
- Back
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What is unique about prokaryotic gene expression
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DNA is not segregated in a nucleus, ribosomes transcribe before mRNA is fully made, control lies in mRNA molecules made
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Define: operon
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Polycistronic genes that control sequences
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Define: repressor
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Proteins produced by regulatory genes -> binds to operator region of specific genes -> prevents mRNA transcription + protein production
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Define: induces
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Small molecules that bind to repressors -> removes repressors ->allows promoter region to be bound by RNA polymerase
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Define: lac operon
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Adjacent genes on a single piece of DNA that codes for 3 different proteins. Used by E.coli to digest lactose
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Define: co-repressor
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A repressor that is inactive by itself thus requires another molecule(co-repressor) to bind before they bind to promoters and prevent transcription
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Define: catabolite repression
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Products of the pathway can activate or inactivate production of proteins. Ie lac operon activity depends on glucose lvl -> ↓ glucose -> ↑ cAMP -> activates CRP -> beta-galactase is made -> ↑ glucose + galactose lvls
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What is the induces of the lac operon?
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Allolactose (co-repressor) that binds to the repressor on the lac operon -> allows binding of RNA polymerase
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Define: attenuation of translation?
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Sequence and structure of mRNA can regulate gene expression(ie when tryptophan is low the mRNA form hair pin thus no protein made, tryptophan is high mRNA changes conformation -> allows transcription of protein
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What is the way gene expression is regulated on histones?
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Histones = basic (+) charge normally + DNA = negative charge -> if u acetylate histones -> turns negative -> allows unwinding of DNA -> and allows proteins to transcribe DNA
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How does alteration of DNA sequence regulates gene expression?
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Used in immunoglobulin's and T-cell receptors -> recombines DNA permanently in cell to produce a specific unique receptor
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How do promoters regulate genes?
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They have regulator elements -> enhancers, silencers, hormone response elements
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How do steroids regulate gene expression?
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DNA regions in the nucleus are bound by Hsp proteins -> when steroids bind to Hsp the DNA region is now exposed -> allows transcription of genes
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How does thyroxine regulate gene expression?
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Thyroid hormone receptor + RXR = thyroxine -> when thyroid hormone binds -> thyroxine changes conformation -> co-activator w/histone acetlase can bind
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How do DNA binding domains regulate gene expression?
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1. Zinc finger - Zinc binds to DNA blocking transcription, 2. leucine zipper - leucine binds to DNA blocking transcription, 3. helix-turn-helix, 4. helix-loop-helix
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Define: regulatory cascade
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ONE transcription factor -> regulates MANY genes
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Function of multiple sites in promoters
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Promoters have several transcription factor binding sites -> directs different activity under different circumstances
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Function of alternative splicing
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Splicing can generate multiple mRNAs -> changes function of product(ie UGT1 gene)
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Function of multiple polyadenylation sites
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Use of site prevents splicing, alters carbody terminus of protein
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Function of mRNA editing
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mRNA sequence that is altered after transcription (ie APOB100 gene -> shorter protein is produce on purpose)
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How is globin regulated?
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↑ heme -> inactivates kinase -> inactivates eIF2 thus??????????????
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Function of blocking translation
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IRE binds to mRNA thus prevents translation -> in presence of Fe2+ -> removes IRE -> allows transcription of ferritin protein
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Function of stability of mRNA?
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Degradation rate of mRNA is important (transferrin receptor mRNA is bound to IRE thus prevents mRNA degradation -> under ↑ [Fe2+] IRE is removed -> allows translation of mRNA -> mRNA is now degraded after use
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