modifying mRNA : introns + exons

• what is the difference between the intital mrna and final mrna

  the initial mrna produced by transcription will be longer
• what is another name for initial mrna

  pre-mrna
• how is pre-mrna different to normal mrna

  pre-mrna requires a sequence of bases to be removed
• what enzyme is used to remove the introns from pre-mrna

  endonuclease
• what are introns


  these are a non-coding nucelic sequences that are removed after transcription
• what are exons


  coding regions that are left behind after the introns are removed
• what happens to the exons after the introns are removed

  the exons are spliced together by an enzyme called ligase to form the final mrna
• what is the function of ligase

  to splice together the remaining exons after the introns are removed
• what is the function of endonuclease

  this enzyme removes the introns from the pre-mrna
• how are prokaryotic and eukaryotic cells different in terms of exons and introns


  prokaryotic cells don't have introns