Blotting The DNA band pattern in the gel is transferred to a thin nylon membrane placed over the ‘size fractionated DNA strand’ by Southern blotting . DNA isolated from blood, hair, skin cells, or other genetic evidences left at the scene of a crime can be compared through VNTR patterns, with the DNA of a criminal suspect to determine guilt or innocence. VNTR patterns are also useful in establishing the identity of a homicide victim, either from DNA found as evidence or from the body itself. The Steps in DNA Fingerprinting technique (Fig.
. ) is as follows: . Extraction of DNA The process of DNA fingerprinting starts with obtaining a sample of DNA from blood, semen, vaginal fluids, hair roots, teeth, bones, etc., . Polymerase chain reaction (PCR) In many situations, there is only a small amount of DNA available for DNA fingerprinting.
If needed many copies of the DNA can be produced by PCR (DNA amplification). Fig. . Schematic representation of DNA fingerprinting : Few representative chromosomes have been shown to contain different copy number of VNTR Chromosome Chromosome Paternal Chromosome Maternal Chromosome Chromosome Chromosome Chromosome Chromosome Chromosome Chromosome Chromosome DNA from crime scene (c) Number of short tandem repeats Amplified repeats, separated by size on a gel, give a DNA fingerprint DNA from individual (A) DNA from individual (B) B A C XII Std Zoology Chapter XII Std Zoology Chapter Molecular Genetics dark bands form a pattern of bars which constitutes a genetic fingerprint.