Southern Blot Technique: 

The Southern blot is one way to analyze the genetic patterns which appear in a person DNA. 

Performing a Southering Blot involves :

Source of DNA : White blood corpuscles, blood, semen, saliva, vaginal swabs, skin cells, bone cells, cells from hair root, etc. are used as a source of DNA for fingerprinting. 

The amount of DNA required can be met by 1 micro gram of tissue or 1,00,000 cells.

• Isolation and Extraction – Isolation of DNA from DNA source cells in a high speed refrigerated centrifuge. 

• DNA Amplification – Many copies of extracted DNA are made by PCR technique. 

• Fragmentation/Digestion of DNA by restriction endonuclease to produce VNTRs. 

• Separation of DNA fragments (VNTRs) by size through gel electrophoresis. 

• Single stranded DNA – Denaturing of VNTRs either by heating or chemically treating the fragments in the gel. 

• Southern Blotting – Transferring (blotting) of separated single-stranded DNA fragments to synthetic membranes such as nitrocellulose or nylon. 

• Hybridisation – Using radioactive/labelled VNTR probe. 

• Exposure to X-Ray films/Autoradiography – Detection of hybridised DNA by autoradiography. 

• After hybridisation autoradiography shows many dark bands of different sizes. 

• These bands give a characteristic pattern for an individual DNA.

DNA prints or DNA profiles of dead bodies are compared with DNA prints of the close, blood relatives (sisters, brothers, parents) to determine the identity of the dead bodies.