The process of genetic fingerprinting

• There are five main stages to genetic fingerprinting : extraction, digestion, separation, hybridisation and development.
• During extraction in genetic fingerprinting, a sample is acquired from an individual, then the DNA is extracted from the sample. The quantity of DNA is then increased using the PCR.
• During digestion in genetic fingerprinting, the DNA is cut into fragments using the same restriction endonucleases, which are selected based on how close they can cut to the target DNA.
• During separation in genetic fingerprinting, the fragments of DNA are separated according to size by gel electrophoresis. The gel is then immersed in alkali to separate the double strands into single strands.
• During hybridisation in genetic fingerprinting, radioactive/fluorescent DNA probes are used to bind with VNTRs. Since the VNTRs and specific DNA probes have complementary bases, they can bind under certain conditions.
• During development in genetic fingerprinting, an X-Ray film is placed over the nylon membrane. This film is exposed by the radiation from the radioactive probes (or positions become visible if fluorescent probes are used). These positions will appear as a series of bars on the gel.
• In order to interpret the results of genetic fingerprinting, the patterns of bars will be passed through an automated scanning machine, which calculates the length of the DNA fragments from the bands. Finally, the odds are calculated of someone else having an identical fingerprint, allowing a person to be identified.