SINEs: Short interspersed repeated elements of the eukaryotic genome.

Much of the eukaryotic genome is composed of a variety of repetitive sequences. Amongst these, there are two kinds of retroposons (sequence elements derived from nonviral cellular RNA): SINEs (short interspersed elements) and LINEs (long interspersed elements). Amplification of SINEs occurs in a single germ cell, and the members of SINEs spread and become fixed in populations through genetic drift. SINEs can be regarded as phylogenetic landmarks: they are specific to one species, a few species, a genus or in some cases a family, indicating a specific time of amplification during evolution. Recent studies concerning the structure and origin of many SINEs revealed that retroposons are more widespread in animal genomes than was previously thought.