dna and protein synthesis

• nucleotide structure

  pentose sugar

  base

  phosphate group
• dna structure

  2 deoxyribose polynucleotide chains

  in a double helix

  with H2 bonds between complimentary base pairs
• DNA replication

  • hydrogen bonds break between bases by dna helicase
  • double helix unzips
  • nucleotide line up along dna strand by complimentary base pairing
  • adjacent nucleotides join and form phosphodiester bonds by dna polymerase
• DNA transcription

  • dna molecule unwinds
  • strands seperate as h2 bonds break
  • antisense strand acts as template for mRNA
  • nucleotides line up along dna via complimentary base pairing
  • RNA polymerase forms mRNA with phosphodiester bonds
• post transcription process:

  • RNA polymerase detaches at terminator region
  • h2 bonds reform
  • dna rewinds
  • splicing occurs (introns removed, exons join)
  • dna moves into ribosome
• dna translation

  • mRNA attaches to ribosome
  • tRNA attaches to specific amino acid
  • tRNA anticodon binds to mRNA codon
  • via complimentary base pairing
  • peptide bonds form
• structure of mRNA

  • long ribose nucleotide
  • single stranded
  • contains nitrogenous bases (C,U,A,G)
• structure of tRNA

  • clover shape
  • single stranded
  • anticodon on one end
  • amino acid binding site on other end
• what is the genetic code?

  sequence of bases coding for a polypeptide. coded in base triplets
• genetic code is...

  • universal - same bases used for all species
  • non overlapping - triplets read one at a time
  • degenerate - more than one triplet codes for same amino acid
• mutations

  • changes in base sequences
  • caused by substitution, insertion and deletion
  • leading to a frame shift