stem junction A collection of nucleotide residues consisting of all and only the nucleotide regions that link more than two unbroken stems such that each region links exactly two unbroken stems. This term is defined relative to the particular unbroken_stems involved and, again, does not imply anything about the pairedness/unpairedness of the bases in this region. The degree of a junction is a property (e.g. 3-junction, 4-junction), so the different degrees do not get separate entries in the ontology. collection of nucleotides residues