Protein synthesis
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Transcript

  • 1. Gene Activity: How Genes Work Mader: Biology 8 th Ed.
  • 2. Outline
    • Function of Genes
      • One Gene-One Enzyme Hypothesis
    • Genetic Code
    • Transcription
      • Processing Messenger RNA
    • Translation
      • Transfer RNA
      • Ribosomal RNA
    Mader: Biology 8 th Ed.
  • 3. Function of Genes
    • Genes Specify a Polypeptide
      • The one gene-one enzyme hypothesis suggests a genetic mutation causes a change in the structure of a protein.
        • A gene is a segment of DNA that specifies the sequence of amino acids in a polypeptide of a protein.
    Mader: Biology 8 th Ed.
  • 4. From DNA to RNA to Protein
    • Central Dogma of Molecular Biology:
      • Genes code for the sequence of nucleotides in RNA molecules.
        • RNA brings about formation of a protein coded for by DNA of a particular gene.
    Mader: Biology 8 th Ed. Transcription DNA Replication mRNA Translation PROTEIN Nucleus Cytoplasm
  • 5. DNA Replication Mader: Biology 8 th Ed.
  • 6. RNA
    • Uracil (U) replaces thymine (T) of DNA.
      • Types of RNA
        • Messenger (mRNA) - Takes message from DNA in nucleus to ribosomes in cytoplasm.
        • Transfer (tRNA) - Transfers amino acids to ribosomes.
        • Ribosomal (rRNA) - Help make up ribosomes.
    Mader: Biology 8 th Ed.
  • 7. Structure of RNA Mader: Biology 8 th Ed.
  • 8. Mader: Biology 8 th Ed.
  • 9. Steps of Gene Expression
    • During transcription , DNA serves as a template for RNA formation.
    • During translation , an mRNA transcript directs the sequence of amino acids in a polypeptide.
    Mader: Biology 8 th Ed.
  • 10. Gene Expression Mader: Biology 8 th Ed.
  • 11. The Genetic Code
    • There is a genetic code for each of the 20 amino acids found in proteins.
      • Genetic code is a triplet code , with each codon consisting of three nucleotide bases.
        • Code Properties
          • Universal
          • Degenerate
          • Unambiguous
          • Contains start and stop signals
    Mader: Biology 8 th Ed.
  • 12. Mader: Biology 8 th Ed.
  • 13. Transcription
    • During transcription, an mRNA molecule is formed with a sequence of bases complementary to a portion of one DNA strand.
      • RNA polymerase joins the nucleotides together in 5’  3’ direction.
        • Promoter defines start of a gene, the direction of transcription, and the strand to be transcribed.
          • Elongation continues until polymerase comes to a DNA terminator sequence.
    Mader: Biology 8 th Ed.
  • 14. Transcription Mader: Biology 8 th Ed.
  • 15. Processing Messenger RNA
    • Newly formed mRNA molecule, primary mRNA transcript, is modified before it leaves the eukaryotic nucleus.
      • Cap on 5’ end, and poly-A tail on 3’ end.
      • Introns are removed during RNA processing, leaving only exons .
        • Mature mRNA
          • In most cases, mRNA splicing is done by a spliceosome.
    Mader: Biology 8 th Ed.
  • 16. Mader: Biology 8 th Ed.
  • 17. Translation
    • Transfer RNA molecules transfer amino acids to the ribosomes.
      • tRNA molecules bind with one particular amino acid, and bear an anticodon complementary to the codon for that amino acid.
        • tRNA synthetases attach correct amino acid to the correct tRNA molecule.
    Mader: Biology 8 th Ed.
  • 18. Transfer RNA Mader: Biology 8 th Ed.
  • 19. Role of Ribosomal RNA
    • Ribosomal RNA (rRNA) is produced off a DNA template in the nucleolus of a nucleus.
      • Packaged with proteins into ribosomal subunits, one larger than the other.
        • Contain binding sites to facilitate complementary base pairing between tRNA anticodons and mRNA codons.
    Mader: Biology 8 th Ed.
  • 20.
    • Ribosomes consist of two subunits.
      • The large subunit has three binding sites for tRNA.
      • The small subunit binds to mRNA.
  • 21. Ribosome Structure and Function Mader: Biology 8 th Ed.
  • 22. Mader: Biology 8 th Ed.
  • 23. A. Initiation Mader: Biology 8 th Ed.
  • 24. B. Elongation Mader: Biology 8 th Ed.
  • 25. Mader: Biology 8 th Ed.
  • 26. C. Termination Mader: Biology 8 th Ed.
  • 27. Online Activities and Tutorials Mader: Biology 8 th Ed. http://learn.genetics.utah.edu/content/begin/dna/transcribe/ http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120077/micro06.swf::Protein%20Synthesis http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter3/animation__mrna_synthesis__transcription___quiz_1_.html http://www.phschool.com/science/biology_place/biocoach/transcription/tcproc.html http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter3/animation__mrna_synthesis__transcription___quiz_2_.html