The invention relates to ribonucleic acids and oligonucleotide probes useful for detection and analysis of microRNA precursors and their targets. The invention furthermore relates to oligonucleotide probes for detection and analysis of other non-coding RNAs, mRNAs, mRNA splice variants, allelic variants of single transcripts, mutations, deletions, or duplications of particular exons in transcripts, e.g., alterations associated with human disease, such as cancer.