A category of polynucleotides, usually from 70 to 500 nucleotides in length. As complexes with proteins (snrps) they have several functions, among them the processing of pre-mRNA, either directly as part of a spliceosome or indirectly by hybridising with the pre-mRNA and altering its architecture, i.e. by altering its secondary structure, its tertiary and quaternary structure is also altered. Some snrps are encoded by their own genes, others by the introns of a host gene which itself has some ribosome-related function.