Non-Coding DNA (AQA A Level Biology): Revision Note

Introns & exons

• The genome within eukaryotic cells contains many non-coding sections of DNA

• Non-coding DNA can be found between genes, as non-coding multiple repeats

  • This means they contain the same base sequences repeated multiple times

• Non-coding DNA can also be found within genes, as introns. These sit in between coding regions called exons

• During transcription, eukaryotic cells transcribe the whole gene (all introns and exons) to produce pre-mRNA molecules

• Before the pre-mRNA exits the nucleus, the non-coding sections (introns) are removed, and the coding sections (exons) are joined together in a process called splicing