lecture_5__05 - Elements of a gene mRNA 5 3 transcription...

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Elements of a gene: ATG TGA start codon (translation start) stop codon promoter transcription start terminator mRNA transcription of a gene starts “upstream” (5’) of the start codon and ends “downstream” (3’) of the stop codon, therefore the coding region is only part of the sequence in a messenger RNA (mRNA) 5 5 3 3 much of the regulation of transcription occurs in the region just upstream of the start codon, called the promoter transcription factors are proteins that bind to the DNA in the promoter and either induce or repress transcription 5 3 mRNA: 5 3 ATG----------------coding----------------------------TAA 5’ untranslated region 3’ untranslated region
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Fig. 17.6 Transcription: a multi-subunit enzyme called RNA polymerase transiently unwinds the DNA helix at the promoter and creates an RNA copy of the gene using one strand of the DNA (the template strand). The mRNA is identical (except for the uracil) to the non-template strand of the DNA. transcription always proceeds from 5’ to 3’ www.rcsb.org/pdb/molecules/ pdb40_1.html
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Transcription initiation: promoter elements (prokaryotes) in prokaryotes, two sequence elements are necessary upstream of the transcription start site (the -10 and -35 elements). RNA polymerase binds to these sequences to initiate transcription. RNA Polymerase is not just one protein but a complex of proteins that binds to the DNA at the promoter. The location of the binding determines which strand will be transcribed and where the start of transcription will be. The binding of RNA polymerase can be affected either negatively or positively by
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lecture_5__05 - Elements of a gene mRNA 5 3 transcription...

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