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Replication, Transcription, and Translation. Corinne Landis Dale S. DiSalvo. The Basics—Eukaryotes vs. Prokaryotes. Eukaryotes . Prokaryotes . Unicellular (small in size) Lack a nucleus with a membrane—nucleoid area instead Lack organelles Replicate via budding or fission Ribosomes

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Replication, Transcription, and Translation


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    1. Replication, Transcription, and Translation Corinne Landis Dale S. DiSalvo

    2. The Basics—Eukaryotes vs. Prokaryotes Eukaryotes Prokaryotes Unicellular (small in size) Lack a nucleus with a membrane—nucleoid area instead Lack organelles Replicate via budding or fission Ribosomes Cytoplasm Chromosomes to carry genes • Multicellular (larger in size) • Nucleus with membrane • Membrane enclosed organelles • Replicate via Mitosis or Meiosis • Ribosomes • Cytoplasm • Chromosomes to carry genes

    3. Eukaryotes

    4. Eukaryotes

    5. Prokaryotes

    6. Prokaryotes

    7. Skeletal Structure IUPAC Name: (2E,4E,6E,8E)-3,7-Dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ol (Retinol) Common Name: Vitamin A Formula: C20H30O

    8. Intermolecular Interactions

    9. Biomolecule :Any molecule produced by a living organism • Carbs • Lipids • Proteins • Nucleic Acids

    10. Carbohydrates

    11. Carbohydrates

    12. Lipids

    13. Lipids

    14. Proteins

    15. Amino Acids

    16. Nucleic Acids

    17. Nucleic Acids—DNA

    18. Central Dogma of Molecular Biology “The central dogma of molecular biology deals with the detailed residue-by-residue transfer of sequential information. It states that such information cannot be transferred back from protein to either protein or nucleic acid.” -Francis Crick

    19. Nucleotides • Building blocks for DNA and RNA

    20. Structure of a Nucleotide • Five Carbon Sugar (Ribose or Deoxyribose) • 1+ Phosphate(s) (no phosphate=nucleoside) • 3’ end: Bears hydroxyl Group (Tail) • 5’ end: Bears phosphate group (Head)

    21. Watson and Crick Base Pairs

    22. DNA vs. RNA

    23. Double Helical B-DNA • Three conformations of DNA found in nature • A, B, Z • B-DNA is prominent in cells • Conformation depends on • hydration level • DNA sequence • the amount and direction of supercoiling • chemical modifications of the bases • the type and concentration of metal ions • presence of polyamines in solution

    24. DNA Replication Purpose: to replicate the entire DNA sequence in preparation for cell division—imperative for growth and repair

    25. Key Enzymes in DNA Replication • Initiator Protein • Helicase • Primase • ssDNA binding proteins • DNA Polymerase • Clamp Protein • Topoisomerase • DNA Ligase • DNA Gyrase

    26. Leading vs. Lagging Strand Leading: 3’ to 5’ direction Lagging: 5’ to 3’ direction

    27. Editing Polymerase I • edits its own errors and those made by other enzymes • 3' --> 5' exonuclease removes incorporation errors using a second active site (editing or proofreading). Products: dNMPs • 5' --> 3' exonuclease activity resides on a separate domain; it removes nucleotides in lengths from 1 to 10 nucleotides.

    28. DNA Replication: Prokaryotes vs. Eukaryotes • Main Difference: Prokaryotic chromosomes have a single origin of replication, while eukaryotic chromosomes have multiple origins of replication.Eukaryotes replicate at several points at the same time.

    29. DNA Replication Video http://www.youtube.com/watch?v=teV62zrm2P0

    30. Cell Cycle

    31. Cell Division—Eukaryotes

    32. Step by Step • Interphase • Prophase • Prometaphase • Metaphase • Anaphase • Telophase &Cytokinesis

    33. Mitosis Video http://www.youtube.com/watch?v=VlN7K1-9QB0

    34. Binary Fission

    35. Step by Step • The bacterium before binary fission is when the DNA tightly coiled. • The DNA of the bacterium has replicated. • The DNA is pulled to the separate poles of the bacterium as it increases size to prepare for splitting. • The growth of a new cell wall begins to separate the bacterium. • The new cell wall fully develops, resulting in the complete split of the bacterium. • The new daughter cells have tightly coiled DNA, ribosomes, and plasmids.

    36. Binary Fission Video http://www.youtube.com/watch?v=DY9DNWcqxI4

    37. Transcription • What is it? – Process by which RNA is synthesized using a DNA template • Why do it? – It lets cells control which genes they are using and when they are using them.

    38. RNA Polymerase • Synthesizes RNA 5’-3’ • “Copies” the template DNA by complimentary base pairing rNTP’s • Able to unwind DNA • No need for single-strand binding protein • Activity is heavily regulated

    39. Transcription: Initiation • Step 1 of the process • RNA polymerase binds to a promoter • TATA Box • Sequence specific promoter • DNA unwinds locally

    40. Transcription: Elongation • rNTP’s enter RNA polymerase active site • rNTP’s are paired to bases of the DNA template • The growing transcript is polymerized 5’-3’ • DNA re-winds behind RNA polymerase

    41. Transcription: Termination • How does RNA Polymerase know when to stop? • Terminator region of the DNA template • Many times, other proteins give RNA polymerase a cue to stop • Poly-A signal (eukaryotes) • Rho dependent termination (prokaryotes)

    42. Special Considerations for Eukaryotes Initiation Processing mRNA gets a 5’ “Cap” and a Poly-A “Tail” Not everything that was transcribed should be translated Introns – “Interfere” Exons – “Expressed” snRNP’s remove the introns from the initial transcript • Upstream control elements • May be thousands of base pairs away • Activator Proteins • Transcription Factors • General • Gene Specific • Bind at the promoter

    43. Eukaryotic Transcription http://www.youtube.com/watch?v=SMtWvDbfHLo

    44. Special Considerations for Prokaryotes Initiation & Elongation Other No “Cap” or “Tail” for mRNA No introns Translation begins before transcription ends • Genes laid out in “operons” • Promoter • Operator – where regulatory proteins will bind • Structural Genes – several individual, but related genes within the same operon • Terminator • Inducible/Repressible

    45. Prokaryotic Transcription http://www.youtube.com/watch?v=oBwtxdI1zvk

    46. Translation • What is it? – the usage of the information encoded on mRNA to synthesize protein • Why do it? – Proteins are necessary for all cellular functions. They must be synthesized according to need. • Translaiton reads mRNA 5’-3’

    47. The Ribosome • The cellular structure responsible for translation • Small and Large subunits • Reads information encoded in mRNA in triplet “Codons” • Obtains amino acids from charged tRNA • Synthesizes the encoded protein from N to C terminus

    48. Codons • Groupings of 3 consecutive bases of mRNA • 1 codon encodes 1 amino acid • Some math tells us… • 3 bases/codon & 4 possible nucleotides/base… • 43 = 64 unique codons • But there are only 20 amino acids! • Each amino acid has multiple corresponding codons • We say the code is “redundant” • 3 codons are “Stop Codons” which tell the ribosome to stop translation