Question

Choose the correct option:

An analysis of chromosomal DNA using the Southern hybridization technique does not use?

• A. Blotting
• B. Autoradiography
• C. Electrophoresis
• D. PCR

Answer 1

The correct option is D

PCR

The correct option is D.

Explanation of correct option:

1. PCR or polymerase chain reaction is used to amplify a small quantity of specific DNA which is used for further characterization.
2. In PCR, the DNA sample is denatured, primers are annealed, and new DNA strands are extended. The amplified sample is further analyzed.
3. This technique is used in biological discoveries, forensics, agriculture, and medical diagnostics.

Explanation of incorrect option:

Option A:

1. Blotting refers to the transfer of DNA molecules/ fragments to a positively charged nylon membrane in Southern blotting.
2. Previously nitrocellulose membranes were used, which was less effective.
3. This process occurs by application of electric field or by capillary action.

Option B:

1. Autoradiography uses radioisotopes like ¹⁴C, ³⁵S, and ³²P that help in determining the position of labeled biological material.
2. These emissions are captured on an X-ray or photographic film during Southern blotting.

Option C:

1. DNA to be analyzed is subjected to the electric field in gel electrophoresis.
2. The separation of molecules occurs based on their size.
3. This is the first step to be carried out after the purification and fragmentation of DNA.

Final answer: An analysis of chromosomal DNA using the Southern hybridization technique does not use PCR.