武汉大学：《遗传学》课程教学课件（英文讲稿）Chapter 08 Gene Expression - The Flow of Genetic Information from DNA to RNA to Protein

Chapter 8 Gene Expression: The Flow of Genetic Information from DNA to RNA to Protein 8-1

8-1 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Gene Expression: The Flow of Genetic Gene Expression: The Flow of Genetic Information from DNA to RNA Information from DNA to RNA to Protein to Protein Chapter 8

Sections to study8.1 Thegenetic code8.2Transcription:FromDNA toRNA8.3Translation:FrommRNA toprotein8.4Differences ingene expression between prokaryotesandeukaryotes8.5 Comprehensive exampie:Computerized analysis ofgene expression in C. elegans8.6 The effect of mutations on gene expression and genefunction8-2

8-2 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Sections to study Sections to study 8.1 The genetic code 8.1 The genetic code 8.2 Transcription: From DNA to RNA 8.2 Transcription: From DNA to RNA 8.3 Translation: From mRNA to protein 8.3 Translation: From mRNA to protein 8.4 Differences in gene expression between prokaryotes 8.4 Differences in gene expression between prokaryotes and eukaryotes and eukaryotes 8.5 Comprehensive example: Computerized analysis of 8.5 Comprehensive example: Computerized analysis of gene expression in gene expression in C. elegans elegans 8.6 The effect of mutations on gene expression and gene 8.6 The effect of mutations on gene expression and gene function function

8.1 The genetic codeA gene's nucleotide seguence is colinear with the aminoacid sequenceofthe encodedpeptide1960s-CharlesYanofsky,E.colitryptophan synthetase subunitTrpA.Isolated a largenumber oftrpAmutants.Build a fine genetic map of trpAmutations.Charles YanofskyPurifiedand determinedamino(1925-)acid sequence of TrpA mutants.8-3

8-3 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display  1960s – Charles Charles Yanofsky Yanofsky, E.coli tryptophan tryptophan synthetase synthetase subunit subunit TrpA.  Isolated a large number of Isolated a large number of trpA mutants. mutants.  Build a fine genetic map of Build a fine genetic map of trpA mutations. mutations.  Purified and determined amino Purified and determined amino acid sequence of acid sequence of TrpA mutants. mutants. 8.1 The genetic code Charles Yanofsky (1925-) A gene’s nucleotide sequence is colinear with the amino acid sequence of the encoded peptide

1 m.u.GeneticmapfortrpAmutationNCPositionofalteredaminoacidintrpApolypeptide2342111152249268111.GyLysGluGlyAminoacidinwild-typepolypeptideM+1.GluAspSTOPAminoacidinmutantpolypeptideValGlnMetArgCys(23)(46)(78)(58)(mutantnumber)Fig.8.48-4

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Evidence that a codon is composed ofmore than one nucleotide20Aminoacids:4 Nucleotides:AlaLeuMGTCIle8-5

8-5 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 4 Nucleotides: Ala Arg Asn Asp Cys Gln Glu Gly His Ile 20 Amino acids: Leu Lys Met Phe Pro Ser Thr Trp Tyr Val A G T C Evidence that a codon is composed of more than one nucleotide

1 nt/a.a.A,G,T,C (4 combinations)2 nt/a.a.AA,AG, AT,ACGA, GG, GT, GCTA, TG, TT, TCCA,CG,CT,CC(4x4-16 combinations)3 nt/a.a.AAA,AAG,AAT,AACAGA.AGG.AGTAGCATA. ATG. ATT, ATCACA, ACG, ACT, ACCGAA, GAG, GAT, GACGGA, GGG, GGT, GGCGTA, GTG, GTT, GTCGCA, GCG, GCT, GCC.....(4x4x4=64combinations)8-6

8-6 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display 1 nt/a.a. A, G, T, C (4 combinations) 2 nt/a.a. AA, AG, AT, AC GA, GG, GT, GC TA, TG, TT, TC CA, CG, CT, CC (44=16 combinations) 3 nt/a.a. AAA, AAG, AAT, AAC AGA, AGG, AGT, AGC ATA, ATG, ATT, ATC ACA, ACG, ACT, ACC GAA, GAG, GAT, GAC GGA, GGG, GGT, GGC GTA, GTG, GTT, GTC GCA, GCG, GCT, GCC . (444=64 combinations)

(a)Colinearityofgenesandproteins1m.u.GeneticmapfortrpAmutationNCPosition of alteredaminoacidintrpApolypeptide23449211115222681LysGluGlyGlyAminoacid in wild-typepolypeptide个.-GluASPCysSTOPArgAminoacidinmutantpolypeptideVal GlnMet(23)(46)(78)(58)(mutantnumber)(b)Recombinationwithinacodon0.001m.u.0.001m.u.codonforcodonforaa211aa234trpA-mutant(Arg)trpAmutant(Cys)2378trpA-mutant(Glu)trpA-mutant(Asp)4658trpA+wild-typerecombinant(Gly)trpA+wild-typerecombinant(Gly)codonforcodonforaa234aa211Fig.8.48-7

8-7 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Fig. 8.4

InterpretationoftheresultsA codon is composed of more than one nucleotideDifferent point mutations may affect the same amino acid.Each nucleotide is part of only a single codon.Each point mutation altered only one amino acid8-8

8-8 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display  A codon is composed of more than one nucleotide. is composed of more than one nucleotide.  Different point mutations may affect the same amino acid. Different point mutations may affect the same amino acid.  Each nucleotide is part of only a single Each nucleotide is part of only a single codon.  Each point mutation altered only one amino acid. Each point mutation altered only one amino acid. Interpretation of the results

Evidence fora triplet code1955-Francis Crick and SydneyBrennerGenerate mutations of bacteriophage T4rllB gene withproflavin.LifeIrcienceSydneyBrennerFrancisCrickSydneyBrenner(1916-2004)(1927-)8-9

8-9 Copyright © The McGraw-Hill Companies, Inc. Permission required to reproduce or display Evidence for a triplet code  1955 – Francis Crick Francis Crick and Sydney Brenner Sydney Brenner  Generate mutations of Generate mutations of bacteriophage bacteriophage T4 rIIB gene with gene with proflavin proflavin. Francis Crick (1916-2004) Sydney Brenner (1927-)

E.coli strainT4strainBK(2)rll+rll-NoplaquesLarge,distinctrll+rll+Small, fuzzySmall, fuzzy8-10

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