Protein Synthesis by babbian

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									From Gene to Protein
       Chapter 17
I. Gene Products
 A. Beadle and Tatum: 1930s
      -One Gene => One Enzyme hypothesis

  B. One Genes One Polypeptide Hypothesis
      -not all proteins are enzymes
      -Quaternary Structure
II. "The Central Dogma"
   -DNA ======> RNA =======> Protein
III. The Genetic Code
    -“Triplet Code” - 3 nucleotides => 1 amino acid
  1. Codons – mRNA triplets
      -transcription
      -complementary to DNA
      -Uracil (no Thymine)
III. The Genetic Code
    -“Triplet Code” - 3 nucleotides specify 1 amino acid
  2. Anticodons – tRNA
      -base pairs with codon - translation
      -links particular codon w/ specific amino acid
III. The Genetic Code
  3. Genetic Code Dictionary
      -LUT - Codon => amino acid
      -“Redundancy but no Ambiguity”
III. The Genetic Code
  3. Genetic Code Dictionary
    a. Start Codon – AUG
        -Methionine
    b. Stop Codons – UAA, UAG, UGA
        -no amino acids
III. The Genetic Code
  3. Genetic Code Dictionary
    c. Reading Frame
        -correct groupings of nucleotides
        -UGGUUUGGCUCA
IV. Transcription – DNA Directed Synthesis of mRNA
 A. Some Terms
IV. Transcription – DNA Directed Synthesis of mRNA
 A. Some Terms
    1. RNA Polymerase
       -unzips DNA
       -assembles RNA nucleotides 5’ to 3’
    2. Promoter
       -DNA sequence where RNA polymerase attaches
       -TATA box
    3. Terminator
       -DNA
IV. Transcription – DNA Directed Synthesis of mRNA
 A. Some Terms
    4. “Downstream” and “Upstream”
        -Downstream = direction of transcription
    5. Transcription Factors
        -proteins - help RNA pol bind/initiate transcription
    6. Transcription Initiation Complex
        -transcription factors + RNA Pol at promoter
IV. Transcription – DNA Directed Synthesis of mRNA
 B. Three Stages of Transcription
   1. Initiation
IV. Transcription – DNA Directed Synthesis of mRNA
 B. Three Stages of Transcription
   1. Initiation
        -TFs bind to TATA
       -RNA Pol binds - unzips DNA
       -TIC
IV. Transcription – DNA Directed Synthesis of mRNA
 B. Three Stages of Transcription
   2. Elongation
       -RNA Pol synthesizes RNA transcript - 5’ to 3’
IV. Transcription – DNA Directed Synthesis of mRNA
 B. Three Stages of Transcription
   3. Termination
       -RNA Pol - hits termination sequence (TTATTT)
       -primary transcript released
V. RNA Processing
     -primary transcript => mRNA
V. RNA Processing
 A. Modification of ends of Primary Transcript
    1. 5’ End
        -Guanine Triphosphate
        -prevents degradation
        -ribosome attaches
V. RNA Processing
 A. Modification of ends of Primary Transcript
    2. 3’ End
       -Poly A tail
       -protects; helps export
V. RNA Processing
 B. RNA Splicing
    1. Introns – “Intervening Sequences” of nucleotides
        -noncoding
        -between coding sequences
    2. Exons – “Expressed Sequences
        -coding segments
V. RNA Processing
 B. RNA Splicing
   3. Spliceosomes
       -proteins + 1o transcript
       -removes introns; splices exons
V. RNA Processing
 B. RNA Splicing
   3. Spliceosomes

     a. small nuclear Ribonucleoproteins (snRNP)– “SNURPS”
         -RNA and protein
V. RNA Processing
 B. RNA Splicing
   4. Ribozymes
       -enzymatic RNA
       -introns can catalyze its own excision
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  A. Transfer RNA – “Interpreter”
    1. Structure
         -clover leaf in 2D
        -single strand of RNA
      a. Amino Acid Attachment site
          -3’ end
      b. Anticodon
          -nucleotide triplet - base pairs w/ codon
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  A. Transfer RNA – “Interpreter”
    2. Wobble Hypothesis
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  A. Transfer RNA – “Interpreter”
    2. Wobble Hypothesis
        -61 codons - 45 tRNA molecules
          -some tRNA bind to 2+ codons
        -flexible base pairing at 3rd codon position
        -Inosine

               Anticodon Base                   Codon Base
                       G                           U or C
                       C                               G
                       A                               U
                       U                           A or G
                       I                         A,U, or C
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  A. Transfer RNA – “Interpreter”
    3. Aminoacyl –tRNA Synthetase
        -binds specific amino acid to tRNA
        -20
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  B. Ribosomes
      -small and large subunits
      -protein and rRNA
    1. Three Sites
      a. A site – Aminoacyl-tRNA Site


      b. P site – Peptidyl – tRNA Sties


      c. Exit Site
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  B. Ribosomes
    2. Polyribsomes
        -strings of ribosomes
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  C. Three Stages of Translation
    1. Initiation
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  C. Three Stages of Translation
    1. Initiation
      a. Sm. Subunit binds to mRNA
          -5' of mRNA
      b. Initiator tRNA binds to mRNA
          -codon AUG
              -TAC – Methionone
      c. Lg subunit attaches
          -initiator at P site
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  C. Three Stages of Translation
    2. Elongation
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  C. Three Stages of Translation
    2. Elongation
      a. Codon Recognition
          -A-site codon H bonds to anticodon on aminoacyl tRNA
      b. Peptide Bond Formation
          -new amino acid (A site) binds to polypeptide chain (P site)
      c. Translocation
          -GTP => GDP
          -ribosome moves tRNAs
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  C. Three Stages of Translation
    3. Termination
VI. Translation – The DNA Directed Synthesis of a Polypeptide
  C. Three Stages of Translation
    3. Termination
        -stop codon - A site => Release Factor
        -subunits disassemble
VII. Protein Synthesis in Eukaryotes vs Prokaryotes
    -prokaryotic ribosomes smaller
    -prokaryotes can simultaneously transcribe and translate from same gene
VIII. Mutations – changes in genetic material of cell
    A. Chromosomal Mutations
        -rearrangement of chromosome
VIII. Mutations – changes in genetic material of cell
    B. Point Mutations
      -one base pair
VIII. Mutations – changes in genetic material of cell
    B. Point Mutations
VIII. Mutations – changes in genetic material of cell
    B. Point Mutations


      1. Types of Point Mutations
        a. Substitutions


        b. Insertions and Deletions
             1) Frameshift Mutation
               -alters Reading Frame
               -insertion/deletion not a multiple of 3
VIII. Mutations – changes in genetic material of cell
    C. Mutagens
        -chemical or physical agents that cause mutations

								
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