Question

The term ‘southern blotting’ refers to
a. Transfer of DNA fragments from in vitro cellulose membrane to electrophoresis gel
b. Attachment of probes to DNA fragments
c. Transfer of DNA fragments from electrophoresis gel to nitrocellulose sheet.
d. Comparison of DNA fragments from two sources

Answer 1

Hint: Southern blotting is also called southern hybridization. DNA probing helps in the detection of nucleic acid in the sample. Then the DNA fragments are separated according to the size of an electrophoresis gel.

Complete answer:
In vitro is the amplification method which artificially synthesizes a probe. It enhances the detection system in the single generated nucleic-acid bases. Option A is incorrect as it does not work in an electrophoresis gel.

The attachment of the probes to DNA fragments can be seen in hybridization allowing many DNA or RNA molecules to allow probes in the detection of nucleic acid in the sample. The main aim of using a DNA probe is to identify the gene or the sequence of chromosomes present in the sample. Option B is incorrect.

The DNA mixture is prepared by breaking it into small fragments. This is the first step in southern blotting. The double-strand DNA gets denatured into single-strands within the gel. In the next step, the DNA is transferred to a blotting membrane called nitrocellulose membrane from the gel. It is labelled as a radioactive probe and can be detected by autoradiography.

After the DNA has formed fragments, it must be purified and separated from other DNA fragments. They can be then compared according to interest.

Hence, the correct answer is option (C).

Note: The DNA fragments are separated according to the size of the gel electrophoresis. Gel electrophoresis is a ubiquitous tool. Blotting is used in molecular biology for identifying nucleic acids and protein.