Which blot technique is used to detect RNA transcripts?

• A. Northern blot detects RNA using RNA or DNA probes; Southern blot detects DNA after restriction digestion with DNA probes.
• B. Northern blot detects DNA fragments with DNA probes.
• C. Southern blot detects protein expression.
• D. Western blot detects RNA.

Answer: (A)

To detect RNA transcripts, you use a blotting method designed for RNA, which is Northern blotting. In this approach, RNA from a sample is first separated by size on a gel, then transferred to a membrane. It’s then hybridized with labeled probes that are complementary to the RNA sequence you’re interested in. Because the probe binds specifically to that RNA, you can see whether the transcript is present and get a sense of its abundance and approximate size. The other blotting methods target different molecules: Southern blot analyzes DNA (often after restriction digestion), and Western blot analyzes proteins using antibodies. So Northern blot is the one that directly identifies RNA transcripts.