noTes

• gene= sequence of nucleotide vases that codes for production of specific amino acid sequence- make up polypeptide protein
• transcription(in nucleus)

  • DNA helicase breaks H+bonds between complementary bases of DNA and DNA unwinds
  • template/antisense strand use to make MRNA molecule
  • free nucleotides line up via complementary vase pairing, adjacent nucleotides join via phosphodiester bonds(catalysed by RNA polymerase)= MRNA strand
  • MRNA moves out of nucleus pore and attaches to ribosome in cytoplasm
• translation

  • MRNA attaches to ribosome
  • TRNA binds to specific amino acids in cytoplasm depending on anticodon
  • complementary anti codon of TRNA binds to codon on MRNA and is held in place by hydrogen bonds
  • ribosome joins the amino acids attached to 2 TRNA molecules by peptide bonds(C reaction) and TRNA molecules detach from amino acid
  • continues until stop codon reached
• nature of genetic code

  • non overlapping= each base only read once and adjacent codons do not share bases
  • degenerate= multiple codons can code for same amino acid, limits effect of mutations
  • triplet code= each 3 bases code for 1 amino acid, start and stop codons