DNA Fingerprinting         

Dr. Alec Jeffreys developed the technique of DNA fingerprinting to identify a person from HIS/HER genetic material.

DNA fingerprinting uses short nucleotide repeats called Variable Number Tandem Repeats (VNTRs) as probe or markers. VNTRs vary from person to person and are inherited from one generation to the next. Only closely related individuals have similar VNTRs.

Technique of DNA fingerprinting:

1) DNA is isolated from blood of person.

2) By the process of polymerase chain reaction (PCR), many copies are produced. This step is called amplification.

3) DNA is cut into small fragments by treating with restriction endonucleases.

4) DNA fragments are separated by agarose gel electrophoresis.
5) The separated DNA fragments are visualized under ultraviolet radiation after applying suitable dye.

6) The DNA is transferred from electrophoresis plate to nitrocellulose or nylon membrane sheet. This is called Southern blotting.

7) Probes are now added which bind to specific nucleotide sequences that are complementary to them. This is called hybridization.

8) The hybridized DNA fragments are detected by autoradiography. They are observed as dark bands on X-ray film.

Explanation of VNTR and Probes:  

VNTR: variable number of tendom repeats. Their hybrids are not possible. They are satellite DNA, and show a very high degree of polymorphism.

Probe: It contains repeated sequence of nucleotides complimentary to each other. Probes are made radioactive and their hybrids are thatswhy possible.

Applications of DNA Fingerprinting

1) It is used as a tool in forensic tests to identify criminals.

2) It is used to settle paternity disputes.

3) It is used to determine population and genetic diversities to study evolution.