Arrange the steps of DNA Fingerprinting in a correct sequence:

(A) Digestion of DNA by restriction endonucleases
(B) Hybridisation using labelled VNTR probe and detection of hybridized DNA by autoradiography
(C) Isolation of DNA
(D) Separation of DNA fragments by electrophoresis and blotting

Choose the correct answer from the options given below:

(C), (A), (D), (B)

The correct answer is Option (2) → (C), (A), (D), (B)

(C) Isolation of DNA

(A) Digestion of DNA by restriction endonucleases

(D) Separation of DNA fragments by electrophoresis and blotting

(B) Hybridisation using labelled VNTR probe and detection of hybridized DNA by autoradiography

DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA, because in these sequences, a small stretch of DNA is repeated many times. These repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation. The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA.

The technique of DNA Fingerprinting was initially developed by Alec Jeffreys. He used a satellite DNA as probe that shows very high degree of polymorphism. It was called as Variable Number of Tandem Repeats (VNTR). The technique, as used earlier, involved Southern blot hybridisation using radiolabelled VNTR as a probe. It included :
(i) isolation of DNA,
(ii) digestion of DNA by restriction endonucleases,
(iii) separation of DNA fragments by electrophoresis,
(iv) transferring (blotting) of separated DNA fragments to synthetic membranes, such as nitrocellulose or nylon,
(v) hybridisation using labelled VNTR probe, and
(vi) detection of hybridised DNA fragments by autoradiography.