The polymerase chain reaction (PCR) technique, developed by Kary Mullis in 1985, is extremely powerful. It generates micro gram quantities of DNA copies (up to billion copies) of the desired DNA segment. At the start of PCR, the DNA from which a segment is to be amplified, an excess of the two primer molecules, the four deoxyriboside triphosphates and the DNA polymerase are mixed together in the reaction mixture that has appropriate quantities of Mg++.
Southern blotting is the transfer of DNA from the gel to the nitrocellulose filter resembles blotting. This technique has been extended to the analysis of RNA (Nothern blotting) and proteins (Western blotting).