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Final Exam Study Guide (got the best grade in class)

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Biological Sciences
BIOL 2153
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Genetics FinalChapter 16Geneticists have learned that highly efficient mechanisms have evolved to turn transcription of specific genes on and off depending on the cells metabolic need for the genes productsRegulationo1 Inducible enzymesProduce certain enzymes only when specific chemical substrates arepresentSubstrate serves as inducerEx Lactose metabolism in E colio2 Repressible the system governing tryptophan expression sufficient supply of tryptophan in environment so no need to expend energy to synthesize enzymes needed for tryptophan productionTryptophan plays a role in repressing the transcription of mRNA needed for producing tryptophansynthesizing enzymesoNegative vs positive controlRegulation whether of the inducible or repressible typeNegative genetic expression occurs unless it is shut off by some form of a regulator moleculePositive transcription occurs only if a regulator molecule directly stimulates RNA productionConstitutive enzymes enzymes that are produced continuously regardless of the chemical makeup of the environment Vibrio choleraeoInfectious gastroenteritisoIngesting contaminated food or wateroInfected patients can die within three hoursEnter stomach V cholerae cells limit protein synthesisMove to small intestine bacteria secrete proteases to break down the mucosal liningReach the intestinal epithelial cells stop making flagellin make and secrete toxinToxin depletes cells of chloride ions secrete water severe dehydrationoAll possible because of gene regulationGene RegulationoControl of gene expression processeso1 TranscriptionalBinding of RNA polymerase to promoterkey step most commonShift from transcriptional initiation to elongationRelease of the mRNA at terminationo2 Posttranscriptionalimpact different phases of pathwaysmRNA stabilityEfficiency of ribosomes recognizing translational signalsPolypeptide stabilityLactose utilization in E coliClassic model for gene regulationoE coli need sugar as a source of carbon and energyoClickerWhich carbon source does E coli preferGlucoseLactose Lactose has to be broken down into glucose firstMade up of galactose and glucoseAdding lactose leads to a 1000fold increase in protein synthesisoThus inducible and lactose serves as the inducerInductionspecific molecule stimulates synthesis of a proteinLacYLacZE Coli will increase protein synthesis for enzymes to breakdown lactoselacZ cleaves lactose into 2 monosaccharidesFigure the catabolic conversion of the disaccharide lactose into is monosaccharide units galactose and glucose The lactose lac operon
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