DnaReference

Definition: A DNA reference is a grouping of several DNA entities that are common in sequence. Members can differ in celular location, sequence features, SNPs, mutations and bound partners. Comments : Note that this is not a reference gene. Genes are non-physical,stateless continuants. Their physical manifestations can span multiple DNA molecules, sometimes even across chromosomes due to regulatory regions. Similarly a gene is not necessarily made up of deoxyribonucleic acid and can be present in multiple copies ( which are different DNA regions).

Source:http://www.biopax.org/release/biopax-level3.owl#DnaReference