Sunday, April 17, 2011

Coding & Non-coding Structures of DNA

Coding structures (Exons)
• These are the parts of the DNA that contain the code for the synthesis of protein or RNA.
• These coding sequences are present within genes.
Non-coding Structures.
• This is DNA that does not contain information for the synthesis of protein or RNA.
• The non-coding sequences are found both between genes and within genes (= introns).
• These non-coding sequences have been termed ‘junk DNA’ but they:
  • Do play a role in gene expression (i.e. whether a gene is switched ‘on’ or ‘off’)
  • Act as spacer material,
  • Permit the synthesis of many new proteins and
  • Play an important role in evolution.
• Non-coding DNA makes up 95% of human DNA.
• Non-coding DNA segments within genes are called introns.

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