Genetic Fingerprinting

• DNA Probes


  Short, single stranded DNA labelled radioactively to locate specific alleles

  • DNA heated, added with probes that are complementary to alleles
  • Identified using X-ray or UV light
• DNA Hybridisation


  DNA heated to seperate the double helix into single strands, then mixed with complementary sequences

  • Once cool, complementary strands will anneal
  • Used in medical diagnosis to identify particular alleles
• Stage 1 - Collection

  Collect the DNA sample

  • Use PCR for amplification
• Stage 2 - Extraction


  Extract DNA from the sample

  • From blood, body cells or hair follicles
• Stage 3 - Digestion


  Restriction Endonucleases added to cut DNA into smaller fragments
• Stage 4 - Seperation (Gel Electrophoresis)


  Samples added to wells in agar gel in a buffer liquid with electrical voltage

  • DNA is negatively charged, so moves to the more positive end of the gel
  • Gel creates resistance, smaller DNA can go further
  • Alkaline added to break up double strands of DNA
• Stage 5 - Hybridisation


  DNA probes (radioactive or fluorescent) added and hybridise with the single stranded DNA
• Stage 6 - Development

  Agar gel will shrink and crack as it dries

  • Transfered to a nylon sheet
  • Exposed to X-rays or UV light
• Stage 7 - Analysis

  Position of the DNA bands are compared to identify genetic relationship between samples and control
• Uses of Genetic Fingerprinting

  • Forensic science
  • Medical diagnosis
  • Breeding relations
• Features allowing Proteins to be seperated:

  • Number of amino acids
  • Charge
  • R groups