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Fig. 8-1

Chapter 8: Transcription and RNA processing. Fig. 8-1. Fundamental chemical distinctions of DNA and RNA. 2’ carbon. Methyl in thymine. pp. 257-8. Fig. 8-3. General types of RNA Informational : mRNA (most diverse) Functional : tRNA rRNA (most abundant) snRNA scRNA.

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Fig. 8-1

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  1. Chapter 8: Transcription and RNA processing Fig. 8-1

  2. Fundamental chemical distinctions of DNA and RNA 2’ carbon Methyl in thymine pp. 257-8

  3. Fig. 8-3

  4. General types of RNA Informational: mRNA (most diverse) Functional: tRNA rRNA (most abundant) snRNA scRNA

  5. Transcription (DNA-dependent RNA synthesis) • Requirements: • RNA polymerase • template DNA (one strand) • ribonucleoside triphosphates (ATP, GTP, CTP, UTP) • assorted cofactors (e.g., Mg++) • Directionality: • RNA always synthesized 5'3' • template DNA is read 3'5' • RNA is complementary to its template DNA

  6. Types of RNA polymerase • Prokaryotes: single enzyme complex • Eukaryotes: three types • Pol I transcribes rRNA genes • Pol II transcribes mRNA genes • Pol III transcribes tRNA, some snRNA genes

  7. Genes may be transcribed from either DNA strand (may be divergently transcribed) Fig. 8-4

  8. Fig. 8-5

  9. Transcription of rDNA genes in amphibian oocyte Fig. 8-6

  10. Polarity and complementarity of DNA and RNA strands Fig. 8-7

  11. Prokaryote 5’-ends & consensus sequences Fig. 8-8

  12. Prokaryote transcription initiation Fig. 8-9

  13. Post-initiation transcription steps Fig. 8-10

  14. Example of a prokaryotic transcription terminator (a hairpin loop structure) Fig. 8-11

  15. Eukaryotic transcription initiation requires the ordered assembly of a preinitiation complex (general transcription factors) (includes specific transcription factors) Fig. 8-12

  16. Pre-mRNA processing in eukaryotes 5’ cap addition (7-methylguanosine addition by guanyltransferase) Splicing to remove introns

  17. Fig. 8-13

  18. Pre-mRNA splicing in eukaryotes Spliceosome:a ribonucleoprotein complex consisting of snRNAs + proteins + pre-mRNA Highly conserved RNA sequences at the intron/exon boundaries  Recruit snRNAs and proteins that assemble into the spliceosome complex  Highly ordered, sequential series of reactions cleave away intron and join together the flanking exons

  19. Common elements of an intron that direct proper splicing Fig. 8-15

  20. Fig. 8-16

  21. Differential splicing creates diverse mRNAs from a single gene Fig. 8-14

  22. Pre-mRNA processing in eukaryotes • 5’ cap addition (7-methylguanosine addition by • guanyltransferase) • Splicing to remove introns • 3’ polyadenylation • - Endonuclease cleavage of pre-mRNA • ~20 nucleotides 3’ to AAUAAA • - Addition of up to several hundreds of A’s • to 3’ end by poly(A) polymerase

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