DNA + Protein synthesis

• Exons=code for protiens
• Introns=non coding regions that are removed from the mRNA transcript during splicing.
• RNA

  Do not contain thymine

  Nucleotides contain pentose sugar

  Single stranded
• DNA

  Contains thymine

  Nucleotides contain deoxyribose sugar

  Double stranded
• What is in a DNA nucleotide

  Phosphate, ester bond, deoxyribose sugar, glycosidic bond, base
• Thymine (T)

  Adenine (A)

  Guanine (G)

  Cytosine (C)

  Uracil(U)
• Amount of bonds in each base pairing

  A-T=2

  G-C=3
• Bond that links nucleotides together

  Phosphodiester
• Transcription

  1. RNA polymerase binds at start codon. DNA helicase breaks hydrogen bonds containing gene for desired protein
  2. RNA moves along template strand, joins free RNA nucleotides to template strand forming pre mRNA
  3. DNA bases re-joined behind RNA polymerase
  4. RNA polymerase stops and detaches at stop codon
  5. Pre-mRNA spliced before leaves nuclear pore to find a ribosome
• Experimental evidence for semi conservative replication

  • Grew two cultures of bacteria in light(N14) or heavy (N15) nitrogen so its incorporated in nucleotides
  • Bacteria grown in N15 put in broth containing N14, meaning if replication was conservative all DNA would contain both
  • Centrifugation
  • Controls N15 lower than N14
  • First gen- in middle
  • Second gen- in middle and same as N14
• DNA polymerase

  • Only complimentary to 3' end of strand
  • Moves along 3' to 5' direction
  • New strand built 5' to 3' direction because the strands are antiparallel
• Translation

  1. Ribosome attaches to start codon on mRNA. tRNA with complementary anti codon with start codon binds to mRNA
  2. Two at a time moves along next codon etc
  3. Condensation reaction between two amino acids=polypeptide bond= forming polypeptide
  4. Goes until stop codon reached and polypeptide formed
• Effects of Mutation

  • Change in primary protein structure
  • COULD code for a different amino acid
  • Sequence of amino acids altered
  • Proteins different or damaged
• Structure of tRNA:

  Short single strand of RNA

  Folded 'clover leaf' shaped held by hydrogen bonds between bases

  Amino acid binding site 3 exposed bases

  Anti codon binding site