Low copy repeats also known as segmental duplications (SDs) for some researchers, are highly homologous sequence elements within the eukaryotic genome. They are typically 10–300 kb in length, and bear >95% sequence identity. Though rare in most mammals, LCRs comprise a large portion of the human genome due to a significant expansion during primate evolution.

Misalignment of LCRs during non-allelic homologous recombination (NAHR) is an important mechanism underlying the chromosomal microdeletion disorders as well as their reciprocal duplication partners. Many LCRs are concentrated in "hotspots", such as the 17p11-12 region, 27% of which is composed of LCR sequence. NAHR and non-homologous end joining (NHEJ) within this region are responsible for a wide range of disorders, including Charcot-Marie-Tooth syndrome type 1A, hereditary neuropathy with liability to pressure palsies, Smith-Magenis syndrome

Smith-Magenis syndrome

Smith–Magenis Syndrome is a developmental disorder that affects many parts of the body. The major features of this condition include mild to moderate mental retardation, distinctive facial features, sleep disturbances, and behavioral problems...

, and Potocki-Lupski syndrome

Potocki-Lupski syndrome

Potocki-Lupski syndrome , also known as dupp11.2p11.2 syndrome, trisomy 17p11.2 or duplication 17p11.2 syndrome, is a contiguous gene syndrome involving the microduplication of band 11.2 on the short arm of human chromosome 17 . The duplication was first described as a case study in 1996...

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