Question

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

Answer 1

Hint: The southern blotting requires a probe strand to form a double-bonded structure with the strand to be identified. A nucleic acid has a double-stranded structure that has a complementary base pairing within the nucleotides.

Complete answer:Southern bolt is one of the many analytical techniques which is used to detect and identify DNA from a given sample. DNA has to be first separated using a special separating technique called electrophoresis which separates DNA according to the molecular weight. After this, the DNA strands are digested with some restriction endonuclease to convert the double-stranded molecules to single-stranded molecules, so that they can form bonds with the complementary probes. Later, these separated and digested segments of DNA are transferred to a membrane. On this membrane, the segments of DNA are allowed to form bonds with the probes which are specially designed, having a complementary sequence to the DNA to be detected. The process where these probes identify the specific DNA and bind to them is called hybridization. This technique is highly specific as the probes will form bonds only with the DNA strands which are complementary to these probes and thus identifies the required DNA fragments only.
Thus, the correct answer is option A. DNA
Additional information: Southern blotting technique is useful in the diagnosis of certain genetic disorders. Also, the detection of DNA has wide applications in fields like forensic science, cancer detection, to resolve parental disputes, etc.

Note: RNA is rarely a double stranded structure. Even though it forms double strands in certain
regions, these bonds are highly unstable. Using techniques like southern blot which need the strand to be identified to make a stable and strong bond with probes cannot be used for identification of single stranded structures like RNA.