1. Unit #3 Schedule: Last Class: – Sanger Sequencing – Central Dogma Overview – Mutation Today: – Homework 5 – StudyNotes 8a Due – Transcription, RNA Processing, Translation Central Dogma Sculpting (Apr 2) – StudyNotes 8b Due Regulation of Gene Expression + Trivia (Apr 4) – StudyNotes 9 Due Tutorial (Apr 5) Review (Apr 9) – Homework 6 Due EXAM 3 (Apr 11)

2. Unpacking Central Dogma: Transcription

3. Learning Objectives: By the end of today’s class you should be able to: 1.Describe transcription. 2.Compare and contrast eukaryotic + prokaryotic transcription. 3.Explain mRNA processing in eukaryotes. 4.Describe the general structure of a tRNA molecule. 5.Discuss the three stages of translation.

4. Fig. 17-3a-2 (a) Bacterial cell TRANSCRIPTION DNA mRNA TRANSLATION Ribosome Polypeptide

5. Fig. 17-3b-3 (b) Eukaryotic cell TRANSCRIPTION Nuclear envelope DNA Pre-mRNA RNA PROCESSING mRNA TRANSLATION Ribosome Polypeptide

6. Synthesis of an RNA Transcript The three stages of transcription: – Initiation – Elongation – Termination Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

7. Fig. 17-7a-4 Promoter Transcription unit DNA Start point RNA polymerase 5 5 3 3 Initiation 3 3 1 RNA transcript 5 5 Unwound DNA Template strand of DNA 2 Elongation Rewound DNA 5 5 5 3 3 3 RNA transcript 3 Termination 5 5 5 3 3 3 Completed RNA transcript

8. RNA Polymerase and Promoter

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11. Prokaryotes vs. Eukaryotes

13. Fig. 17-9 Transcription Termination in Eukaryotes: Transcribes the sequence AAUAAA Signals for the RNA transcript to be cleaved.

14. Transcription Termination Sequences In Prokaryotes, transcription stops by way of as transcribed terminator. This is part of the transcription sequence that signals RNA polymerase to detach. (Hairpin theory) In Eukaryotes, transcription stops when a polyadenylation signal AAUAAA occurs. Proteins then cleave the RNA transcript off.

15. Transcript Processing

16. Fig. 17-3b-3 (b) Eukaryotic cell TRANSCRIPTION Nuclear envelope DNA Pre-mRNA RNA PROCESSING mRNA TRANSLATION Ribosome Polypeptide

17. Fig. 17-9 Protein-coding segment Polyadenylation signal 3 3 UTR5 UTR 5 5 Cap Start codon Stop codon Poly-A tail G PPPAAUAAA AAA …

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19. Fig. 17-10 Pre-mRNA mRNA Coding segment Introns cut out and exons spliced together 5 Cap Exon Intron 5 1 30 31104 ExonIntron 105 Exon 146 3 Poly-A tail 5 Cap 5 UTR3 UTR 1 146

20. Fig. 17-11-1 RNA transcript (pre-mRNA) Exon 1Exon 2Intron Protein snRNA snRNPs Other proteins 5

21. Fig. 17-11-2 RNA transcript (pre-mRNA) Exon 1Exon 2Intron Protein snRNA snRNPs Other proteins 5 5 Spliceosome

22. Fig. 17-11-3 RNA transcript (pre-mRNA) Exon 1Exon 2Intron Protein snRNA snRNPs Other proteins 5 5 Spliceosome components Cut-out intron mRNA Exon 1 Exon 2 5

23. Minute Paper: We have ~20,000 genes yet we can make ~100,000 different protein products. How is this possible if DNA  RNA  Protein?

24. Fig. 17-3b-3 (b) Eukaryotic cell TRANSCRIPTION Nuclear envelope DNA Pre-mRNA RNA PROCESSING mRNA TRANSLATION Ribosome Polypeptide

25. Alternative Splicing Some genes can encode more than one kind of polypeptide, depending on which segments are treated as exons during RNA splicing. Such variations are called alternative RNA splicing. Because of alternative splicing, the number of different proteins an organism can produce is much greater than its number of genes. Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings

26. Translation

27. Fig. 17-3b-3 (b) Eukaryotic cell TRANSCRIPTION Nuclear envelope DNA Pre-mRNA RNA PROCESSING mRNA TRANSLATION Ribosome Polypeptide

28. Fig. 17-3a-2 (a) Bacterial cell TRANSCRIPTION DNA mRNA TRANSLATION Ribosome Polypeptide

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32. Translation

33. Transfer RNA (tRNA) bridges RNA language and amino acid language

34. Transfer RNA (tRNA) Single-stranded RNAs of about 74 - 95 nucleotides – On one “end”, they hold an amino acid – On the other “end”, they bind to mRNA There are about 45 different tRNAs in eukaryotic cells

35. tRNA Structure Campbell 8e, Fig. 17.14

37. “Charging” Transfer RNA Aminoacyl tRNA Synthetase Specific for particular pairs of amino acids and tRNA Requires ATP Campbell 8e, Fig. 17.15

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39. Ribosomes and the Mechanism of Translation

40. Ribosomes and Translation Three Stages of Translation Initiation Elongation Termination

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43. Elongation

44. © 2011 Pearson Education, Inc. Termination

45. Campbell 8e, Fig. 17.21 Signal Peptides

46. Coming Up: Tuesday: -Molecular Sculpting: -Translation, transcript processing, translation -StudyNotes 8b is due.