Non-coding DNA

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•  Some regions of DNA do not code for proteins but have other important functions

The vast majority of the human genome is comprised of non-coding DNA (genes only account for ~ 1.5% of the total sequence)

  • Historically referred to as ‘junk DNA’, these non-coding regions are now recognised to serve other important functions
  • Examples include satellite DNA, telomeres, introns, ncRNA genes and gene regulatory sequences 

Types of Non-Coding DNA

non-coding DNA

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•  Tandem repeats are used in DNA profiling

DNA profiling is a technique by which individuals can be identified and compared via their respective DNA profiles

  • Within the non-coding regions of an individual’s genome there exists satellite DNA – long stretches of DNA made up of repeating elements called short tandem repeats (STRs) 
  • Tandem repeats can be excised using restriction enzymes and then separated with gel electrophoresis for comparison
  • As individuals will likely have different numbers of repeats at a given satellite DNA locus, they will generate unique DNA profiles
    • Longer repeats will generate larger fragments, while shorter repeats will generate smaller fragments

Comparative STR Lengths at Two Specific Loci