Question

Arrange the following steps of DNA fingerprinting in their correct sequence.

• A. I, II, IV, V, III
• B. II, V, III, IV, I
• C. II, IV, V, III,I
• D. V, II, III, IV, I

Answer 1

The correct option is C II, IV, V, III,I

DNA fingerprinting is a laboratory technique which relies on the DNA of a person to determine his/ her unique identity. The DNA fingerprint of two individuals is different due to the variations in their genetic makeup.
The procedure of DNA fingerprinting is as follows:-

1. Isolation of DNA: Since the DNA content of every cell is the same, hence it can be extracted from the samples available like blood, saliva, semen, hair follicle etc.
2. Polymerase Chain reaction: Amplification of DNA is done by Polymerase Chain reaction to increase its quantity.
3. Restriction digestion: Cleavage of DNA is done by using restriction enzymes which yields DNA fragments
4. Gel electrophoresis: These DNA fragments are then transferred to Agarose gel for gel electrophoresis. This leads to separation of DNA fragments of varying sizes which then get arranged according to their molecular weight.
5. Southern Blotting: The separated DNA fragments present in the gel are transferred to a nylon or nitrocellulose membrane, the process called southern blotting. Treatments are given so as to get single strands out of the double stranded DNA that got transferred onto the membrane.
6. Hybridisation: To detect the presence of repetitive site locus, a single stranded radioactive probe or fluorescent probe is used which is complementary to satellite sequence. The probe is then allowed to hybridise with the DNA on the membrane.
7. Autoradiography: Lastly, the nylon or nitrocellulose membrane is exposed to X-rays. Specific bands appear on the X ray film corresponding to the areas of hybridisation

So the most appropriate option is c here.