Restriction Fragment Analysis This technique enables researchers to compare the DNA of different individuals. This technique makes use of Gel Electrophoresis, except that it hybridise the separated DNA fragments with a radioactive probe. Procedures Electrophoresis The two or more samples of DNA to be compared are separated by electrophoresis, on the same piece of gel. Each of them will form a characteristic pattern of bands. Blotting A sheet of nitrocellulose paper is pressed onto the gel. Capillary action will pull the separated fragments onto the paper, in such a way that they are positioned in bands exactly as on the gel. Hybridisation The paper blot is exposed to a solution that contains radioactive labeled probe. The probe is single stranded DNA complementary to the DNA sequence of interest, and it will pair complementarily with the separated fragments.  Auto-radiography A sheet of photographic film is laid on the paper. The radioactive probe will cause images to show up at places where there are DNA fragments. These images can be compared to tell the difference between the samples of DNA being analysed.   Relating Topics - Gel Electrophoresis