Question

Southern blotting procedure does not include:

• A. Digestion and separation of DNA fragments using agarose gel electrophoresis.
• B. Ligation of the target DNA into a cloning vector.
• C. Transfer of DNA fragments to a nitrocellulose membrane.
• D. Hybridization of the membrane with a labelled probe.

Hint:

Remember the purpose of the main DNA techniques:

\textbf{Cloning/Ligation}: To build or create new DNA molecules.
\textbf{PCR}: To amplify or make many copies of DNA.
\textbf{Southern Blot}: To detect or find a specific DNA sequence. \end{itemize}

Answer 1

The Correct Option is B

Step 1: Concept Overview:
Southern blotting is a technique to detect specific DNA sequences within a DNA mixture. The question requires identifying a step NOT involved in this technique.

Step 2: Detailed Explanation:
The standard Southern blot steps are:
1. Digestion and Separation: DNA is digested with restriction enzymes into fragments, then separated by size using agarose gel electrophoresis. (Corresponds to option A).
2. Transfer (Blotting): DNA fragments are transferred from the gel to a membrane (nitrocellulose or nylon). (Corresponds to option C).
3. Hybridization and Probing: The membrane is incubated with a labeled DNA probe complementary to the target sequence. The probe hybridizes to the target fragment if present. (Corresponds to option D).
4. Detection: The bound probe's location is visualized, revealing the target DNA fragment's presence and size.
- Option (B), "Ligation of the target DNA into a cloning vector," is used in molecular cloning for creating recombinant DNA. Southern blotting is an analytical/detective process, not a constructive one.

Step 3: Final Answer:
Ligation into a cloning vector is not a Southern blotting step. Therefore, option (B) is correct.