Splicing of pre-mRNA

• In prokaryotes, transcription results directly in the production of mRNA from DNA (no splicing)
• In eukaryotes, transcription results in the production of pre-mRNA, which is then spliced to form mRNA
• Splicing:

  DNA contains regions called exons (that code for proteins) and regions of DNA called introns that do not code for proteins
• Splicing:

  DNA contains regions called exons (that code for proteins) and regions of DNA called introns that do not code for proteins

  • These intervening introns would prevent the synthesis of a polypeptide
• Splicing:

  In pre-mRNA both exons and introns are present, but the introns must be 'spliced out' (removed) to only leave exons
• Splicing:

  • The base sequences corresponding to the introns are removed and the functional exons are joined together
  • This happens in eukaryotes ONLY as prokaryotes don't have introns