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TRANSCRIPTION

1. TRANSCRIPTION. 2. TRANSCRIPTION RNA STRUCTURE, SYNTHESIS, AND FUNCTION Kinds of RNA transfer, ribosomal, messenger Structure single-stranded, partial double-strand regions, H bonds RNA Polymerase Promoter reading frame, closed complex, open complex, initiation

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TRANSCRIPTION

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  1. 1 TRANSCRIPTION

  2. 2 TRANSCRIPTION RNA STRUCTURE, SYNTHESIS, AND FUNCTION Kinds of RNA transfer, ribosomal, messenger Structure single-stranded, partial double-strand regions, H bonds RNA Polymerase Promoter reading frame, closed complex, open complex, initiation Specificity Factor sigma Polymerization single strand 5' > 3' Termination Eukaryotic mRNA exon, intron, capping, poly A, splicing RNA POLYMERASE ACTIVITY SUBJECT TO: Specificity factors sigmas which recognize specific promoters Accessory factors repressors, activators, anti-sense RNAs, anti-sigma factors

  3. 3 GENE PRODUCTS INCLUDE: PROTEIN OR RNA GENES (DNA) TRANSCRIPTION BY RNA POLYMERASE mRNA or rRNA or tRNA TRANSLATED INTO PROTEINS FUNCTION IN PROTEIN SYNTHESIS

  4. 4 URIDINE TRIPHOSPHATE - UTP ESTER URACIL N - GLYCOSIDE BOND ANHYDRIDES NUCLEIC ACID BASE RIBO NUCLEOSIDE RIBO NUCLEOSIDE TRIPHOSPHATE OR: RIBONUCLEOTIDE

  5. 5 RNA STRUCTURE SINGLE STRANDS COMPLEMENTARY REGIONS FOLD BACK PARTIALLY DOUBLE-STRANDED

  6. 6 [POLYCISTRONIC]

  7. 7 RNA POLYMERASE + PROMOTER CLOSED COMPLEX DOUBLE STRAND OPEN COMPLEX PROMOTER UNWOUND RNA POLYMERASE SUBUNITS a2bb' s CORE - POLYMERIZATION INITIATION (SPECIFICITY) FACTOR HOLOENZYME FUNCTIONS : RECOGNIZE/BIND SUBSTRATES - ATP, GTP, UTP, CTP PROMOTER - SITE IN DNA TEMPLATE - TRANSCRIBES NUCLEOTIDE SEQUENCE INITIATION OF POLYMERIZATION

  8. 8 PROMOTER - SITE IN DNA RNA POLYMERASE BINDS; STARTS TRANSCRIPTION -35 -10 +1 5' 3' 3' 5' 5' 3' 3' 5' ONE DNA STRAND IS TEMPLATE (TRANSCRIBED) RNA SEQUENCE - COMPLEMENTARY TO LOWER DNA STRAND; IDENTICAL TO TOP STRAND (EXCEPT U FOR T) RNA - POLYMERASE STARTS CHAINS

  9. 9 RNAPOLYMERIZATION 3' 5' DNA TEMPLATE 3' 3' 5' 5' NUCLEOTIDYL TRANSFER 3' 5' NOTE 5' 3' + 3' 3' 5' 5'

  10. 10 GENE OR OPERON PROMOTER TERMINATOR 5' 3' 3' 5' TRANSCRIPTION START TRANSCRIPTION STOP RNA POLYMERASE HOLOENZYME - CORE + s RNA POL CLOSED COMPLEX CORE + s OPEN COMPLEX ATP/GTP/UTP/CTP 3' 5' INITIATION

  11. 11 PPi +s ATP/GTP/UTP/CTP 3' 3' 5' POLYMERIZATION 5' 3' 3' 5' 5' 3' 5' TERMINATION

  12. 12 TERMINATOR STEM AND LOOP COMPLETED mRNA PROTEIN CODING REGION PROTEIN READING FRAME 5' 3' UNTRANSLATED REGION

  13. 13 GENE OR OPERON PROMOTER TERMINATOR 5' 3' 3' 5' TRANSCRIPTION START TRANSCRIPTION STOP TRANSLATION START TRANSLATION STOP

  14. 14 GROWTH IS DYNAMIC PROCESS – REPLICATION & TRANSCRIPTION GO ON SIMULTANEOUSLY

  15. 15

  16. 16 EUKARYOTE M-RNA PROCESSING +1-TRANSCRIPTION START TRANSLATION STOP TRANSCRIPTION STOP TRANSLATION START DNA POLY A ADDITION SITE PROMOTER NON - PROTEIN CODING INTRON PROTEIN CODING EXON PRIMARY TRANSCRIPT PRE-M-RNA 5' 3' EXON INTRON 5' CAPPING 3' POLY ADENYLATION

  17. 17 AAAA A AAAA A 5' 3' CAP SPLICING (SPLICEOSOME) POLY-A MATURE M-RNA PROTEIN CODING REGION [CONTIGUOUS CODONS] TRANSLATION PROTEIN

  18. 18 CAP 3' CAP FUNCTIONS - STABILITY DIRECT RIBOSOMES TO START CODON NEAREST CAP

  19. 19 TRANSCRIBING RNA POLYMERASE II (YEAST) CUT AWAY • ENTERING DNA BINDS CLEFT (POSITIVE CHARGES) • CLAMP FOLDS OVER • TEMPLATE AND NON - TEMPLATE STRANDS SEPARATED • WALL BENDS DNA TEMPLATE 90o , EXPOSES RNA 3' END • Mg2+ ACTIVE SITE • SUBSTRATE NTPs ENTER FUNNEL AND PORE • RNA: DNA 9 BP HYBRID • RUDDER SEPARATES RNA: DNA HYBRID TRANSCRIPTION

  20. TAKE HOME: RNA POLYMERASE SEPARATES DNA DOUBLE HELIX AND COPIES NUCLEOTIDE SEQUENCE OF GENES FROM ONE STRAND OF DNA INTO COMPLEMENTARY STRAND OF RNA. WHY? FOR LIFE TO GO ON, INCLUDING PRODUCTION OF DESCENDANTS, THE GENETIC PROGRAM OF THE CHROMOSOME MUST BE RUN. THE FIRST STEP IS TO COPY THE NUCLEOTIDES SEQUENCE OF EACH GENE INTO MESSENGER RNA. THE SECOND STEP WILL BE TO USE THE MESSENGERS FOR SYNTHESIS OF ALL PROTEINS, INCLUDING ENZYMES AND STRUCTURAL PROTEINS, NECESSARY TO CATALYZE ALL REACTIONS OF LIFE AND TO FORM ALL THE CELL STRUCTURES.

  21. 20 RNA POLYMERASE ACTIVITY • SPECIFICITY - DEPENDS ON SIGMAs • DIFFERENT SIGMA FACTORS ALLOW CORE ENZYME TO TRANSCRIBE DIFFERENT SETS OF GENES • DIFFERENT SETS OF GENES HAVE DIFFERENT PROMOTERS RECOGNIZED BY DIFFERENT SIGMA FACTORS • E. COLI HAS 7 SIGMAs ACCESSORY PROTEINS MODULATE ACTIVITY OF RNA POLYMERASE AND SIGMA - REGULATE LEVEL • INCLUDE REPRESSORS AND ACTIVATORS • ANTI - SENSE RNA • ANTI - SIGMA FACTORS

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