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: Understanding the Concept:
Southern blotting is a molecular biology technique used to detect a specific DNA sequence within a complex mixture of DNA. The question asks to identify a step that is NOT part of this analytical procedure.

Step 2: Detailed Explanation:
The standard steps of a Southern blot are:
1. Digestion and Separation: The DNA sample is first digested into smaller fragments using restriction enzymes. These fragments are then separated by size via agarose gel electrophoresis. (This matches option A).
2. Transfer (Blotting): The separated DNA fragments are transferred from the gel to a solid membrane (like nitrocellulose or nylon). (This matches option C).
3. Hybridization and Probing: The membrane is incubated with a labeled DNA probe that is complementary to the target sequence of interest. The probe will bind (hybridize) to the target fragment if it is present. (This matches option D).
4. Detection: The location of the bound probe is visualized, revealing the presence and size of the target DNA fragment.
- The step described in option (B), "Ligation of the target DNA into a cloning vector," is a key step in molecular cloning or creating recombinant DNA. It is a constructive process, whereas Southern blotting is a purely analytical/detective process.

Step 3: Final Answer:
Ligation into a cloning vector is not part of the Southern blotting procedure. Therefore, option (B) is the correct answer.