Genetic Fingerprinting

• Genetic fingerprinting is the analysis of variable tandem repeats (VNTRs). They repeat over an over but do not code for anything.
• Collection and extraction


  If a DNA sample is too small, PCR used. DNA can be used from hair follicles, blood, body cells, etc...
• Digestion


  restriction endonucleases is used to cut either end of the VNTRs
• Separation


  Gel electrophoresis is used. DNA starts in the wells at the negative end (DNA negatively charged due to phosphate groups), smaller VNTR pieces move faster and further, alkaline then added to separate the strands.
• Hybridisation


  different DNA probes (short single stranded DNA with complementary base sequence to the VNTR, probes are radioactively or fluorescently labelled) mixed with single stranded DNA VNTRs on the agar gel for them to bind.
• Development


  VNTRs and DNA probes moved to a nylon sheet and exposed to x-ray or UV light to visualise the position.
• Analysis


  Position of the DNA bands compared to identify genetic relationship, presence of disease causing genes and used for forensics on crime scenes.