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SURVEY OF BIOCHEMISTRY Transcription and Translation

Learn about the processes of transcription and translation in biochemistry, including DNA-binding motifs, amino acids, initiation, elongation, termination, and gene organization.

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SURVEY OF BIOCHEMISTRY Transcription and Translation

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  1. SURVEY OF BIOCHEMISTRYTranscription and Translation

  2. PRS Which of the following is not an example of a DNA-binding motif in proteins? • Beta Sheet • Helix-turn-Helix • Zinc Finger • Leu Zipper

  3. PRS • Which amino acid contains a hydroxyl in its side chain? • Threonine • Methionine • Aspartic Acid • Phenylalanine

  4. Transcription Transcription is the process by which RNA is producedfrom a DNA template. • Initiation • Elongation • Termination Steps involved intranscription

  5. Transcription DNA has to separate at the position where transcription occurs. Fig. 26-3

  6. Transcription Sense Strand 5’-…GATCCGTAGGTC…-3’ 3’-…CTAGGCATCCAG…-5’ Antisense Strand(template) Newly synthesizedRNA has the same general sequence as the sense strand; U in RNA, T in DNA 5’-…GATCCGTAGGTC…-3’ 5’----GAUCCGUAGGUC…3’ 3’-…CTAGGCATCCAG…-5’

  7. Transcription Initiates at Promoter Sequences What is a gene? Example of E.coli Lactose Operon Organization Fig. 26-4 P: Promoter O: Operator I: Inhibitor

  8. Structural genes follow promotersequences In E. coli, the lactose operon consists of 3 structural genes: • Beta-Galactosidase (Z) • Galactoside Permease (Y) • Thiogalactoside Transacetylase (A)

  9. E. coli Promoter Sequences Notice how sequence is numbered! Usuallysingle purine

  10. = sigma factor Prokaryotic RNA Polymerases The sigma factor bindsspecifically to the promoter.Core enzyme affinity to DNA ~5x10-12 M. Core enzyme Holoenzyme

  11. Elongation: RNA Chain Growth 3’-OH group acts as a nucleophile, attacking the alpha phosphate group, with subsequent release of inorganic pyrophosphate.

  12. DNA Supercoiling Negativesupercoiling Positivesupercoiling RNA polymerase is processive Once an RNAP has moved from the promoter, another can bind Transcription is fast: constitutive enzymes vs. inducible enzymes

  13. Termination of Transcription Because the newly synthesized RNA is single-stranded,hairpin structures can easily form from the termination sequence.

  14. Hairpin Structure in RNA What happens when a known terminator sequence is missing? G-C richbp region Poly-U tail

  15. Termination: Rho Factor Helicase: RNA-RNA and RNA-DNA complex unwinding.

  16. Transcription in Eukaryotes • RNA Polymerase I • Precursors to rRNA • RNA Polymerase II • Precursors to mRNA • RNA Polymerase III • Precursors to 5S rRNA, tRNA • Precursors to other small RNA’s

  17. Eukaryotic Transcription Factors Transcription factors are req’d to initiate transcription,and facilitate elongation in eukaryotes. Eukaryotic Termination: Not well understood

  18. Portion of the Genetic Code Wobble

  19. Reading Frames

  20. Translation: Protein Synthesis • Messenger RNA • Template • Transfer RNA • Carries amino acids • Ribosomal RNA • Aids protein synthesis

  21. tRNA Structures 3D 2D

  22. tRNA’s have modified bases Be able to name, draw, recognize structures fromFigure 27-4.

  23. Aminoacyl tRNA Synthetases Aminoacyl tRNA synthetases add aa’s to tRNA. Step 1.

  24. Aminoacyl tRNA Synthetases Step 2. +tRNA

  25. Ribosome

  26. Sites in the Ribosome A Aminoacyl PPeptidyl EExit E P A

  27. Chain Initiation in Translation Start Codon: AUG Methionine

  28. Shine-Dalgarno Sequence upstream downstream

  29. Initiation

  30. Translation: Polypeptide Synthesis PeptidylTransferaseActivity

  31. Elongation

  32. Administrative Updates • Exam 1 on Thursday, 4-5 pm • 20 questions • Short answers and Multiple Choice • Closed-book • Calculators allowed • No cell phones, blackberries, etc. • Office Hours: M, T, R 2-4 pm

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