Describe The Central Dogma Of Molecular Biology.

Module 3F – Protein SynthesisProtein Synthesis Sofar in this unit, we have examined: How genes are transmitted from onegeneration to the next WhereWh genes are llocatedd What genes are made of How genes are replicated How damaged genes are repaired Inthis, the final module of theunit, we will examine how genesworkrk tot controlntr l theth geneticn ti traitstr itof organisms.12Objective # 32Objective 32 AccordingDescribe the central dogmaof molecular biology.3Objective 32to the central dogma ofmolecular biology,biology, the flow ofinformation in cells is from DNA, toRNA, to proteins. Basically, genes control the traits oforganisms by controlling whichproteins are made. Although there are exceptions, ingeneral, each gene codes for theproduction of one polypeptide.4Objective 32The process of protein synthesis can bedivided into 2 stages: transcription andtranslation.1) During transcription,transcription, DNA is usedas a templatet mpl t tot makem k 3 typest p offRNA:2) During translation,translation, the 3 types ofRNA (mRNA, rRNA, and tRNA)are used to link amino acidstogether in the correct sequence inorder to produce the desiredprotein.a) messengermessenger--RNA (mRNA)b) ribosomalribosomal--RNA (rRNA)c) transfertransfer--RNA (tRNA)561

Objective # 33Name the 3 types of RNAinvolved in protein synthesis andbriefly describe the structure andfunction of each.7Objective 338The sequence of bases on the mRNA is acode that determines the sequence ofamino acids in the polypeptide beingsynthesized: MessengerRNA (mRNA) is a single,long, unbranched, and uncoiled chainof RNA nucleotides. The sequenceqof bases on the mRNAmolecule is a code which specifies thesequence for joining amino acidstogether in order to form a g RNAEach group of 3 bases on themRNA molecule codes for aparticular amino acidMetProHisArgAspAlaSerAmino acids join to forma polypeptide chainCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.910During protein synthesis, the 2 ribosomalsubunits join with a molecule of mRNAand then read the code on the mRNA inorder to form a polypeptide:Objective 33 RibosomalRNA (rRNA) also consistsof a long, unbranched chain of RNAnucleotides. It joins with proteins toform the ribosomal subunits. Each ribosome is composed of 2subunits – a large subunit and a smallsubunit.subunit Eukaryotic ribosomal subunits arelarger than those found in prokaryotes.Sectional plane90 LargeLsubunitSectioned ribosome3 Smallsubunit0 11LargesubunitSmallsubunitCopyright The McGraw-Hill Companies, Inc. Permissionrequired for reproduction or display.Largesubunit3 SmallsubunitmRNA5 mRNA5 122

Objective 33Objective 33 TransferRNA (tRNA) is composed ofa long unbranced chain of RNAnucleotides that is coiled into a specific3-dimensional shape:2D “Cloverleaf” Model 3D Ribbon-like ModelAcceptor3 5 endAnticodonloopAcceptor endAnticodon loopCopyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.3D Space-filled ModelAcceptor endAnticodon loop SpecialIconAcceptor endAnticodon endenzymes called aminoacylaminoacyl-tRNAsynthetases attach an amino acids to theacceptor end of each tRNA molecule. A tRNA with an amino acid attached iscalled a “charged”charged tRNA The tRNA then brings the amino acidto the ribosome where it is linked withother amino acids according to thesequence specified by the mRNA.1314Objective # 34In detail, describe the process oftranscription in prokaryotic cellsincl ding initiation,includinginitiation elongation,elongationand termination.1516Objective # 35In detail, describe the process oftranslation in prokaryotic cellsi l di iinitiation,includingii ielongation,liand termination.17183

Objective 35 Thenext 3 slides provide a moredetailed look at the 3 stages oftr n l ti n in prtranslationprokaryotick r ti cells:ll19202122Objective # 36Explain how protein synthesis ineukaryotes differs from proteinsynthesis in prokaryotes.prokaryotes23244

2526Objective 36Objective # 37Describe and be able to use thebase pairing rules for DNA toDNA, DNA to RNA, and RNA toRNA.A AAlso bbe ableb to use thecodon/amino acid dictionary totranslate a segment of mRNA.2728Objective 37Objective 37DNADNAATTAGCCGDNAATGCRNAUACGRNAAUGCRNAUACG Thecodon/amino acid dictionaryshows us which amino acid eachcodon codes for:29305

Objective # 38Explain and give examples ofthe following types ofmutations:a)) PointP i mutationsib) Chromosomal mutations 3132Objective 38 aObjective 38 amutations involve alterations inthe structure or location of a singlegene. Generally, only one or a few basepairs are involved.p Point mutations may be caused byphysical damage to the DNA fromradiation or chemicals, or may occurspontaneously.Types of point mutations include: Substitutions – the replacement of oneor more base pairs with different pairs. PointOriginal GTCAATGTCAAAT3334Objective 38 a Additionsor insertions – the additionof one or more base pairs to a gene.35Original TCGAATGTCGAAAT366

Objective 38 aObjective 38 a Transpositions– the movement of agene from one location to anotherwithin the genome. Deletions– the removal of one ormore base pairs from a gene.Original AATOriginal12New13323738Objective 38 aObjective 38 b Transposonsare small segments ofDNA capable of moving at randomfrom one location to another withinthe genome of a single cell. When a transposon is inserted into agene at a new location, this oftendestroys the disrupted gene’s function.This is called insertional inactivation.inactivation. Chromosomalmutations involve largescale changes in the structure of achromosome (affecting many genes),orr changeshiin ththe numbermb r offchromosomes present (extra ormissing chromosomes).3940Objective 38 bObjective 38 b Chromosomalmutations include: Deletions – a piece of a chromosomeis lost entirely:OriginalNewAABCC Duplications– a piece of achromosome duplicates itself so thattwo or more copies are present:DOriginalDNew41ABABCBDCD427

Objective 38 bObjective 38 b Inversions– the gene order in asegment of the chromosome isreversed:OriginalNew TranslocationsABCDEADCBE– a piece of achromosome breaks off and attachesto a different chromosome. Aneuploidyp– the ppresence of one ormore extra chromosomes. Polyploidy - the presence of one ormore extra sets of chromosomes.4344Objective # 39Explain how the following types ofpoint mutations can alter the structureof a polypeptide chain:substitutioninsertiondeletion.4546Objective 39Objective 39 Substitutionsthat change a codon forone amino acid into a different codonfor the same amino acid are calledsilent mutations:mutations: Substitutionsthat change a codon forone amino acid into a codon for adifferent amino acid are calledmissense mutations:mutations:OriginalSubstitutionDNA TACAGCTTA TACAGTACAGTTTTAmRNA AUGAUGUCGUCGAAUAAU AUGAUGUCAUCAAAUAAUOriginalSubstitutionDNATACAGCTTA TACATACACCCTTAmRNA AUGAUGUCGUCGAAUAAU rSer-Asp47MetMet-SerSer-AspMetMet-TryTry-Asp488

Objective 39Objective 39 Substitutionsthat change a codon forone amino acid into a stop codon arecalled nonsense mutations:mutations: TheOriginalSubstitutionDNATACAGCTTA TACATACATTCTTAmRNA AUGAUGUCGUCGAAUAAU 9genetic code does not contain anypunctuation marks to show where onecodon ends and another begins. Therefore, insertions or deletions thatdo not involve multiples of 3 base pairswill change the reading frame of thegene, and alter all codons downstreamfrom the mutation. These are calledframeshift mutations:50Objective 39DNAOriginalInsertionTACAGCTTATACTACTTAGCTTAmRNA AUGUCGAAU lu51529

The process of protein synthesis can be divided into 2 stages: transcription and translation. 5 as a template to make 3 types of RNA: a) messengermessenger--RNA (mRNA)RNA (mRNA) b) ribosomalribosomal--RNA (rRNA)RNA (rRNA) c) transfertransfer--RNA (tRNA)RNA (tRNA) Objective 32 2)2) During During translationtranslation, the