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12–3 RNA and Protein Synthesis12-3 RNA and Protein SynthesisSlide1 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein Synthesis12–3 RNA and ProteinSynthesisGenes are coded DNA instructions that control theproduction of proteins.Genetic messages can be decoded by copying partof the nucleotide sequence from DNA into RNA.RNA contains coded information for making proteins.The Structure of RNA RNA consists of a long chain of nucleotides. Each nucleotide is made up of a 5-carbon sugar,a phosphate group, and a nitrogenous base.Slide2 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisThe Structure of RNAThere are three main differences between RNA andDNA: The sugar in RNA is ribose instead ofdeoxyribose. RNA is generally single-stranded. RNA contains uracil in place of thymine.Slide3 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTypes of RNATypes of RNAThere are three main types of RNA: messenger RNA ribosomal RNA transfer RNASlide4 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTypes of RNAMessenger RNA (mRNA) carries copies ofinstructions for assembling amino acids intoproteins.Ribosomes are made up of proteins andribosomal RNA (rRNA).During protein construction, transfer RNA(tRNA) transfers each amino acid to theribosome.Slide5 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranscriptionTranscriptionRNA molecules are produced by copying part of anucleotide sequence of DNA into a complementarysequence in RNA. This process is calledtranscription.Transcription requires the enzyme RNApolymerase.Slide6 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranscriptionDuring transcription, RNA polymerase binds toDNA and separates the DNA strands.RNA polymerase then uses one strand of DNAas a template from which nucleotides areassembled into a strand of RNA.RNA polymerase binds only to regions of DNAknown as promoters.Don King – Boxing “Promoter”Promoters are signals in DNA that indicate tothe enzyme where to bind to make RNA.Slide7 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranscriptionRNARNA polymeraseDNASlide8 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisRNA EditingRNA EditingThe DNA of eukaryotic genes containssequences of nucleotides, called introns,that are not involved in coding for proteins.The DNA sequences that code for proteinsare called exons.When RNA molecules are formed, intronsand exons are copied from DNA.Slide9 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisThe introns are cutout of RNAmolecules.RNA EditingExon IntronDNAPre-mRNAThe exons are thenspliced together toform mRNA.mRNA* Therefore, exonswill be expressed asgenes!CapCopyright Pearson Prentice HallTailSlide10 of 39

12–3 RNA and Protein SynthesisThe Genetic CodeThe Genetic CodeThe genetic code is the “language” of mRNAinstructions.The code is written using four “letters” (the bases:A, U, C, and G).A codon consists of three consecutive nucleotideson mRNA that specify a particular amino acid.Slide11 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisThe Genetic CodeEach codon specifies a particular amino acid thatis to be placed on the polypeptide chain.Some amino acids can be specified by more thanone codon.Slide12 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisThe Genetic CodeThere is one codon AUG that can either specifythe amino acid methionine or serve as a “start”codon for protein synthesis.There are three “stop” codons that do not code forany amino acid. These “stop” codons signify theend of a polypeptide.Slide13 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranslationTranslationTranslation is the decoding of an mRNAmessage into a polypeptide chain (protein).Translation takes place on ribosomes.During translation, the cell usesinformation from messenger RNA toproduce proteins.Slide14 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranslationMessenger RNA is transcribedin the nucleus, and then entersthe cytoplasm where it attachesto a ribosome.NucleusmRNASlide15 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranslationTranslation begins when an mRNA moleculeattaches to a ribosome.As each codon of the mRNA molecule movesthrough the ribosome, the proper amino acid isbrought into the ribosome by tRNA.In the ribosome, the amino acid is transferredto the growing polypeptide chain.Slide16 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranslationEach tRNA molecule carries only one kind ofamino acid.In addition to an amino acid, each tRNAmolecule has three unpaired bases.These bases, called the anticodon, arecomplementary to one mRNA codon.Slide17 of 39Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranslationThe ribosome binds new tRNA molecules and aminoacids as it moves along the Slide18 of 39Start codonCopyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisTranslationProtein SynthesisLysinetRNATranslation directionmRNARibosomeCopyright Pearson Prentice HallSlide19 of 39

12–3 RNA and Protein SynthesisTranslationThe process continues until the ribosome reachesa stop codon.PolypeptideRibosometRNASlide20 of 39mRNACopyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisThe Roles of RNA and DNAThe Roles of RNA and DNAThe cell uses the DNA “master plan” to prepareRNA “blueprints.” The DNA stays in the nucleus.The RNA molecules go to the protein building sitesin the cytoplasm—the ribosomes.Genes and ProteinsGenes contain instructions for assembling proteins.Many proteins are enzymes, which catalyze andregulate chemical reactions.Proteins are each specifically designed to build orSlide21 of 39operate a component of a living cell.Copyright Pearson Prentice Hall

12–3 RNA and Protein SynthesisCodonThe sequence ofbases in DNA is usedas a template formRNA.Genes and ProteinsCodon CodonSingle strand of DNACodon Codon CodonThe codons of mRNAspecify the sequenceof amino acids in aprotein.mRNAAlanine Arginine LeucineAmino acids withina polypeptideCopyright Pearson Prentice HallSlide22 of 39

12–3Click to Launch:Continue to:- or -Slide23 of 39Copyright Pearson Prentice Hall

12–3The role of a master plan in a building is similarto the role of which molecule?a. messenger RNAb. DNAc. transfer RNAd. ribosomal RNASlide24 of 39Copyright Pearson Prentice Hall

12–3A base that is present in RNA but NOT in DNA isa. thymine.b. uracil.c. cytosine.d. adenine.Slide25 of 39Copyright Pearson Prentice Hall

12–3The nucleic acid responsible for bringingindividual amino acids to the ribosome isa. transfer RNA.b. DNA.c. messenger RNA.d. ribosomal RNA.Slide26 of 39Copyright Pearson Prentice Hall

12–3A region of a DNA molecule that indicates to anenzyme where to bind to make RNA is thea. intron.b. exon.c. promoter.d. codon.Slide27 of 39Copyright Pearson Prentice Hall

12–3A codon typically carries sufficientinformation to specify a(an)a. single base pair in RNA.b. single amino acid.c. entire protein.d. single base pair in DNA.Slide28 of 39Copyright Pearson Prentice Hall

12 –3 RNA and Protein . Biology Autho

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