How do Southern blotting and Northern blotting differ?

How do Southern blotting and Northern blotting differ?

• A. Southern blot detects RNA; Northern blot detects DNA.
• B. Southern blot detects DNA fragments; Northern blot detects RNA.
• C. Southern blot detects DNA fragments using DNA probes after restriction digestion; Northern blot detects RNA using RNA or DNA probes.
• D. Southern blot detects proteins; Northern blot detects lipids.

Answer: (C)

The main idea here is how Southern and Northern blotting differ in what they detect and how they detect it. In Southern blotting, you start with DNA, usually by cutting genomic DNA with restriction enzymes to create fragments of various sizes. Those fragments are separated on a gel, transferred to a membrane, and then probed with a DNA probe that is complementary to the sequence of interest. If the target DNA fragment is present, the probe hybridizes to it and you can detect it. In Northern blotting, you’re looking at RNA. RNA is separated by size on a gel, transferred to a membrane, and then probed with something complementary to the RNA—this probe can be either RNA or DNA. This reveals which RNA transcripts are present and their sizes. Option that states these details is the best because it precisely captures both the target material (DNA fragments after restriction digestion for Southern; RNA for Northern) and the nature of the probes used (DNA probes for detecting DNA in Southern; RNA or DNA probes for detecting RNA in Northern). The other statements misstate what each blot detects or omit the probe types, and one option is about proteins and lipids, which is not relevant to these RNA/DNA blotting techniques.

The main idea here is how Southern and Northern blotting differ in what they detect and how they detect it. In Southern blotting, you start with DNA, usually by cutting genomic DNA with restriction enzymes to create fragments of various sizes. Those fragments are separated on a gel, transferred to a membrane, and then probed with a DNA probe that is complementary to the sequence of interest. If the target DNA fragment is present, the probe hybridizes to it and you can detect it. In Northern blotting, you’re looking at RNA. RNA is separated by size on a gel, transferred to a membrane, and then probed with something complementary to the RNA—this probe can be either RNA or DNA. This reveals which RNA transcripts are present and their sizes.

Option that states these details is the best because it precisely captures both the target material (DNA fragments after restriction digestion for Southern; RNA for Northern) and the nature of the probes used (DNA probes for detecting DNA in Southern; RNA or DNA probes for detecting RNA in Northern). The other statements misstate what each blot detects or omit the probe types, and one option is about proteins and lipids, which is not relevant to these RNA/DNA blotting techniques.