Low copy repeats (LCRs), also known as segmental duplications (SDs), or duplicons, are DNA sequences present in multiple locations within a genome that share high levels of sequence identity.
The repeats, or duplications, are typically 10–300 kb in length, and bear greater than 95% sequence identity.
Though rare in most mammals, LCRs comprise a large portion of the human genome owing to a significant expansion during primate evolution.
Misalignment of LCRs during non-allelic homologous recombination (NAHR)[3] is an important mechanism underlying the chromosomal microdeletion disorders as well as their reciprocal duplication partners.
[4] Many LCRs are concentrated in "hotspots", such as the 17p11-12 region, 27% of which is composed of LCR sequence.