What does northern blotting primarily detect?

Northern blotting is a technique specifically designed for the detection of RNA molecules. It involves the separation of RNA samples by gel electrophoresis, followed by transferring the RNA onto a membrane and hybridizing it with a labeled probe that is complementary to the target RNA sequence. This allows for the visualization of specific RNA transcripts within a complex mixture.

The primary utility of Northern blotting lies in its ability to provide information about gene expression levels. By analyzing the size and abundance of specific RNA molecules, researchers can infer which genes are actively transcribed under certain conditions, making it a powerful tool in molecular biology and genetic research.

In contrast, other techniques are employed for the detection of DNA (like Southern blotting), proteins (such as Western blotting), and carbohydrates. Each of these assays targets different types of biomolecules and utilizes distinct methodologies suited to their specific properties. Thus, Northern blotting's specificity for RNA is what makes the answer clear and justifies it as the correct choice.