transcription

• transcription is the first stage of protein synthesis
• 1)RNA polymerase attaches to DNA

  • RNA polymerase attaches to double helix and the H bonds between 2 DNA strands of a gene break
  • DNA helix uncoils
  • one strand is used as a template to make mRNA copy
• 2) complementary mRNA is formed

  • RNA polymerase lines up free RNA nucleotides along template strand
  • complementary base pairing
  • once RNA nucleotides have paired there joined together by RNA polymerase
  • form mRNA strand
• 3) RNA polymerase moves down the DNA strand

  • RNA polymerase moves along DNA assembling mRNA strand
  • H bonds between uncoiled DNA strands re-form once RNA polymerase has passed by
  • strands coil back into double helix
• 4. mRNA leaves the nucleus

  • when RNA polymerase reaches a stop codon, stops making mRNA and detaches from DNA
  • mRNA moves out nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm
  • next stage