Question

Some of the steps of DNA fingerprinting are given below. Identify the correct sequence from the options given :
A. Electrophoresis of DNA fragments
B. Hybridisation with DNA probe
C. Digestion of DNA by RENs
D. Autoradiography
E. Blotting of DNA fragments to nitrocellulose membrane

• A. A - C - E - D - B
• B. A - E - C - B - D
• C. C - A - E - B - D
• D. C - A - B - E - D

Answer 1

Answer: (C)

DNA fingerprinting is the technique for identifying individuals, generally using repeated sequences in the human genome that produce a pattern of bands which is unique for every individual. Important for DNA fingerprinting are short nucleotide repeats that vary in number from person to person, but are inherited. These are the Variable Number of Tandem Repeats or VNTRs. The VNTRs of two persons may be of the same length and sequence at certain sites, but vary at others.
The techniques has following steps:
(i) Isolation of DNA from sample cell.
(ii) If DNA is less in amount, it can be amplified using polymerase chain reaction (PCR).
(iii) Digestion of this DNA by restriction endonucleases or RENs (C).
(iv) These DNA fragments are electrophoresed in agarose gel. These fragments can be visualised using EtBr-UV system (A).
(v) Separated DNA fragments are transferred to nitrocellulose membrane using Southern Blotting (E).
(vi) Probing for VNTRs is done using labelled DNA probes (B).
(vii) The hybridised fragment can be detected by autoradiography (D).
This technique can be used in doing paternity tests, identification of criminals, etc.