Genetic Fingerprinting

• The pattern is unique to every individual
• 1. DNA to be investigated is amplified by PCR.

  • Primers can be sequenced so they attach either side of the VNTRs.
  • They can also carry a 'marker' making them visible.
• 2. The amplified DNA of the 'variable number tandem repeat sequence' region can be digested by restriction endonuclease
• 3. The digested DNA is injected into wells on the electrophoresis gel to separate out the fragments by size, using an electrical current. The VNTRs being DNA, have a negative charge so move through the gel towards the positive electrode.

  The smaller DNA fragments move faster to move further. The bonds can be viewed under UV light or via their fluorescence (from the primers) they can then be compared with other genetic fingerprints.
• 4. Hybridisation

  If specific base sequences are being looked for the DNA can be made single stranded using an alkali solution then radioactive or fluorescent probes bind to the VNTRs. Different probes bind to different target, DNA sequences.
• 5. Development

  Photogenic film is put over a nylon sheet which has had the probes stuck to it. The radioactive probes expose it to show the bonding. If done using fluorescent probes, then they can be identified without the use of this.
• In forensic science

  Allows DNA at a crime scene to be compared with that of a suspect/ from a database
• In medical diagnosis

  Comparisons between regions with faulty alleles of parents and the genetic fingerprints of IVF pre-implantation embryos; or that of DNA known to cause cancer to the genetic fingerprint of a patient.
• In animal and plant breeding

  Reduces inbreeding and therefore genetic disorders by choosing individuals to mate whose genetic fingerprints are least similar