translation翻译过程.ppt

Translation OncetheDNAcodehasbeenTranscribedontoamRNAmolecule mRNAleavesthenucleusandmovesintothecytoplasm InthecytoplasmthemRNAcombineswiththeRibosomestomakeEnzymes Proteins TheProcessofreadingthemRNAcodeandbuildinga n Enzyme ProteiniscalledTranslation orProteinSynthesis InorderforTranslation ProteinSynthesistooccuracellneeds 1 mRNA carryingtheDNAcode 2 Ribosomes3 AminoAcids4 tRNA picksupaminoacidsinthecytosolandcarriesthemtotheribosomeswheretheywillbejoinedtogethertoformaProtein ThemRNAismadeintheNucleusthroughtheprocessofTranscription mRNAismadeupofRNAnucleotides Eachgroupof3nucleotidesiscalledaCodonandcodesforoneaminoacidofthenewlyformingProtein ThisSegmentofamRNAmoleculeis7codonslong 21nucleotides andwillcodefor7aminoacids Ribosomes theribosomesaretheactualsiteofTranslation proteinsynthesis MadeintheNucleolus madeupofRibosomalRNA rRNA AnimalsandPlantsgettheiraminoacidsthesamewaytheygettheirNucleotides TransferRNA tRNA tRNAisasmall foldedRNAchain 74 93nucleotides thatpicksupandtransfersspecificaminoacidstoagrowingpolypeptidechainattheribosomalsiteofproteinsynthesisduringtranslation IthassitesforAminoAcidattachmentandanAnticodon TheAnticodoniscomposedofcomplementarybases EachtRNAmoleculebindstoonlyonetypeofaminoacid MorethanonetRNAexistsforeachaminoacid SummaryofTranslation or soyouwanttomakeaProtein Let sbegininthenucleus TheDNAhasthecodetoinstructtheRibosomesastowhichProteinstomake Ok 2problemshere 1 theDNAisintheNucleusandtheribosomesareintheCytoplasm and2 theribosomescan treadtheDNA Wellthere saneasywaytofixbothproblems it scalledTranscription ThroughTranscription theDNAcodeisplacedontoamRNAmoleculewhichcan1 leavethenucleus travelintothecytoplasmandjoinwiththeribosomes and2 theribosomescanTranslate read themRNA SonowwehavetheDNAcode bywayofmRNA inthecytoplasmthatcaninstructtheRibosomesastowhichproteintomake Bytheway thedifferencebetweenoneproteinandanotherproteinistheorderoftheaminoacids thenumberofaminoacidsandits3dimensionalshape Now let ssayyouarearibosome youarejustsittingaround inthecytoplasm waitingforsomeaminoacidstoassembleintoprotein youalreadyhavetheinstructions rememberthemRNA butyoucan tgettheaminoacidsyourself youneedhelp youneedtRNA ThetRNAcanpickupspecifiedaminoacids andbringthemtoyouinthecorrectorder buthowdoesIknowwhichaminoacidtopickup ThetRNAknowswheretoplaceitsaminoacidbecausethetRNAcanreadthemRNAcodon themRNAcodonisatranscribedversionoftheDNAcode itinstructsthemRNAastowhereitshouldplacetheaminoacid Bytheway thefirstaminoacidisalwaysmethionine orsometimesreferredtoas f met So It sthissimple you reatRNAmolecule Youhaveanaminoacidattachedtoyou yousimplymoveupordownthemRNAlookingfortherightplacetodropoffyouraminoacid you lleasilyrecognizewheretoplacetheaminoacid it swhereyouranticodonmatchesthemRNAcodon Thisprocesswillcontinueuntila terminationorstop codon locatedonthemRNA instructstheribosomestobreakapart endingtranslation Translation 1stletter Row2ndLetter Column3rdLetter Sentence GeneRegulation Somegenescanbe switchedon or switchedoff Whenageneisswitchedon aproteinisproduced whenageneisswitchedoffaproteinisnolongerproduced Howtheorganismisaffecteddependsontheprotein AnOperonisageneswitch itislocatedontheDNA Whatanoperonreallyisisaseriesofgenesthatcodeforaparticularprotein Thefirstoperondiscoveredisknownasthe lac operon Thelac Operon Thelac OperonFourregionsofDNAcontroltheproductionofaproteinsuchastheenzymeBeta galactosidease whichisusedtodigestlactose astructuralgenethatcodesfortheenzymeBeta galactosidease 2 anoperatorregionrightinfrontofthestructuralgene wheretherepessormoleculeattachestopreventTranscription 3 apromoterregionwheretheRNAPolymerasebindstotheDNA 4 aregulatorgenewhichcodesfortheRepressor 5 Arepressorisamoleculewhichbindstotheoperatorandpreventstranscription Thecombinedregionoftheoperatorandstructuralgeneiscalledanoperon regulatorgene DNA Lac operon EditingDNA About65 ofanorganism sDNAisnotused it sleftoverbaggagefromevolution Asaconsequence about65 ofthemRNAtranscribedisalsouseless SothemRNAmustbe edited toremovetheuselesscodes Thiseditingisaccomplishedbyenzymes ThepiecesofmRNAwhicharesplicedoutarecalledIntrons ofcoursetheycannotcodeforanything ThepiecesofmRNAwhichareleftin afterediting arecalledExons ofcoursetheyaretheexpressedcodes ExamplesofGenescontainingExonsandIntrons TheStructureofaChromosome ChromosomeMaps Adiagramthatshowsthelocation locus plural loci ofagene MUTATIONS ThereplicationofDNAisusuallyextremelyaccuratebecauseDNApolymeraseproof readstheDNAasitisproduced Ifnecessary DNApolymeraseremovestheincorrectnucleotideandreplacesit IftheDNAisNOTrepairedaMutationwilloccur AmutationisachangeintheDNA Thischangewillaffecttheproteinwhichisproducedandcaneventuallyaffecttheorganism straits The2mostcommoncausesofmutationsare Radiation suchasultravioletandx ray and VariousreactivechemicalscalledCarcinogens IftheMutationoccursinaSomaticcellorbodycell itisnotinheritable IftheMutationoccursinagamete itisheritable TypesofMutations ChangesintheDNAaffectingtheresultingtraits The2mostcommonmutationsare 1 PointMutations2 Frame shiftMutations PointMutation Changesinonenucleotideinthegeneticcode Effects nonetofatal Example SickleCellAnemia SickleCellAnemia FrameShift Imagineasentenceshouldread theredcatatetherat Ifadeletionoccurs aletterisremoved inthiscasethefirstletter e thesentencewouldread thredcatatatherat Theadditionofaletter inthiscasetheletter o wouldresultwithaframeshiftwhichlookslikethis thoeredcatatatherat Insertions Deletions TheadditionorlossofabaseintheDNAWhichcausesaframeshiftmutation Biotechnologies CloningTheHumanGenomeProjectGeneSplicing Whatare RestrictionEnzymes andwhataretheyusedfor GeneTherapy