Question

The Southern blot technique is used for the detection of
A. DNA
B. RNA
C. Protein
D. RNA and DNA

Answer 1

Hint:- In modern molecular biology, scientists use a special technique called blotting to identify specific biomolecules in a sample. There are different blotting techniques to detect different target molecules. Dr. Edwin Southern developed the first blotting technique known as Southern blot.

Complete step-by-step solution:- Southern blot is a technique used for the detection of a specific DNA sequence in a sample of blood or tissue. First, DNA is isolated from the given sample. It is then fragmented into small bits using a specific restriction endonuclease. This process is called restriction enzyme digestion. Next, the DNA fragments are sorted according to their length using gel electrophoresis. The medium used in gel electrophoresis is Agarose obtained from the seaweed red algae belonging to the family Gelidiaceae. Since, DNA is a negatively charged particle, DNA fragments show migration in presence of an electric field. Small fragments will move faster through the porous gel towards anode while, the bigger fragments will take time to move. This causes the formation of a band of DNA fragments in the gel. Sodium hydroxide is used to denature the DNA into single strands. After this the bands are transferred to a membrane called blotting paper with the help of an electrical gradient. The pattern of DNA fragments on the gel remains the same after transfer to the membrane. Next, a single stranded DNA probe labelled with a radioactive tag is introduced into the blot. The DNA probe will pair with complementary DNA sequences on the gel to form a double-stranded DNA. Now the probe can be located in the gel using X-ray films.
So the correct answer is (A), DNA.

Note:-
The technique of Southern blot is used in a number of applications like, identification of a single gene in DNA fragment pool, detection of specific DNA sequences in a genome, gene mapping, detection of chromosomal aberrations, genetic diseases and cancers, DNA fingerprinting and forensic tests.