分子生物学分子生物学 (1).ppt

Chapter 2Genes and GenomesGregor MendelGregor Mendel 1822-1884 1822-18841865,Mendel put forward the theory of genetic factors2.1.1 Development of the concept of genes2.1 The Concept and Structure of Genes Wilhelm Johannsen Wilhelm Johannsen 1857 1857 1927 1927In 1909,Johannsen replaced genetic factors with genes1910,T.H.Morgan confirmed that the gene is on the chromosome Thomas H.Morgan(1866-1945)1941，G.W.Beadle&E.L.Tatum The genetic control of the biochemical reaction in Alternaria alternata proposes the theory of one gene and one enzyme.1944，M.McCarty&O.AveryPneumococcal transformation experiments proved that DNA is genetic material.1952，A.Hershey&M.ChaseT4 bacteriophage infection bacterial experiment confirmed that DNA is genetic material.HemoglobinOne gene,one polypeptide chainOne gene,one polypeptide chain2.1.2 The concept of genes All All DNA DNA that that synthesizes synthesizes functional functional proteins proteins or or RNA RNA(except(except RNA RNA viruses),viruses),including including nucleic nucleic acid acid sequences sequences encoding encoding proteins proteins or or RNA RNA and and regulatory regulatory sequences sequences necessary necessary to ensure transcriptionto ensure transcriptionDNAgene(1)Structural gene(1)Structural gene(2)Non-structural genes(2)Non-structural genes 2.1.3 The structural of genes A A noncoding noncoding segment segment(flanking(flanking sequence)sequence)of of DNA DNA on on either either side side of of a a structural structural gene gene involved involved in in the the regulation of gene expression.regulation of gene expression.DNA DNA sequences sequences that that can can be be transcribed transcribed into into mRNA,mRNA,encoding RNA or protein polypeptide chains.encoding RNA or protein polypeptide chains.DNA intron exon The structural genes of prokaryotes are continuous,The structural genes of prokaryotes are continuous,and RNA synthesis does not require splicing processing.and RNA synthesis does not require splicing processing.The structural genes of eukaryotes are composed of The structural genes of eukaryotes are composed of exon and intron.The coding sequence is discontinuous and exon and intron.The coding sequence is discontinuous and is called the is called the split genesplit gene.(1)Structural gene(1)Structural geneRNA splicingMature mRNAmRNA precursor(2)Non-structural genes(2)Non-structural genes TATAAATATAAAATATTTATATTT 5 533 3 3 5 5 transcriptionstart point 3Non-structural genes are DNA sequences that do not encode RNA or protein polypeptide chains and participate in the transcriptional regulation of structural gene expression,also known as cis-acting elements.The types of cis-acting elements Promoter and upstream promoter elementsResponse elementEnhancerSilencerPoly(A)tail signalPromoter and upstream promoter elementsPromoter and upstream promoter elements-25-25+1+1transcriptionstart pointPromoter:RNA polymerase specifically recognizes the DNA sequence that binds and initiates transcription,is directional,and is located upstream of the transcription start site.TATA Box,about-25 bp upstream of the transcription start point,the core sequence TATA(A/T)A(A/T),combined with TATA binding protein to start gene transcription.-globin gene promoter mutation:TATAA TGTAA,reduce the transcription efficiency of mRNA -thalassaemia.upstream promoter element -25-25+1+1-70-70transcription start pointThe specific DNA sequence upstream of the TATA box is specifically combined with the trans-acting factor to regulate the transcription efficiency of the gene.CAAT box(CAAT box):located at about-70 bp,the core sequence is GGNCAATCT.Combined with CTF to regulate transcription efficiency.GC boxGC box：Located at about-120 bp,the core sequence Located at about-120 bp,the core sequence CCGCC binds to the transcription factor SP1 to CCGCC binds to the transcription factor SP1 to promote the transcription process.promote the transcription process.Response elementResponse elementCAAT boxTATA box promoter 3response element exon intron exon intron exon5 Specific Specific DNA DNA sequences sequences that that can can bind bind to to activated activated information information molecule molecule receptors receptors and can regulate gene expression.and can regulate gene expression.Alpha-fetoprotein(AFP)gene glucocorticoid response element:-181 -161 cccaaagagctctgtgtcctThe enhancer can combine with trans-acting factors to enhance transcription activity,and it is effective and non-directional in any position of the gene.Silencer gene expression negative regulatory elements,combined with trans-acting factors,inhibit transcriptional activity.Alpha-fetoprotein(AFP)gene silencer:-317 -301 5-cttcattaacttaattt-3Prothrombin gene enhancer:-922 -897,5-GTGTTCCTGCTCTTTGTCCCTCTGTC-3Enhancer Silencer5-AATAAA-GTGT-3DNA mRNA precursor5-AAUAAA-GUGU-35-AAUAAA-AAAAAAAA 3 mRNA The AATAAA sequence of the structural gene conserved end and the downstream GT or T-rich region are recognized by polyadenylation specific factors,and about 200 As are added at the 3 end of the mRNA.Poly(A)signalBeta globin gene Poly(A)signal mutation:AATAAA AACAAA,+thalassaemia.The continuous coding sequence between the translation start codon and the stop codon in the gene is called an open reading frame(open reading frame,abbreviated as ORF).The 5 non-coding region of mRNA is between the transcription start site and the translation initiation codon,and the 3 non-coding region is the sequence between the translation stop codon and the transcription termination site (untranslated regions,abbreviated as UTR).open reading frame(ORF)untranslated regions(UTR)Thank You