Sister chromatid exchange (SCE) is the exchange of genetic material between two identical sister chromatids.
It was first discovered by using the Giemsa staining method on one chromatid belonging to the sister chromatid complex before anaphase in mitosis. The staining revealed that few segments were passed to the sister chromatid which were not dyed.
The Giemsa staining was able to stain due to the presence of bromodeoxyuridine analogous base which was introduced to the desired chromatid.
The reason for the (SCE) is not known but it is required and used as a mutagenic testing of many products. Four to five sister chromatid exchanges per chromosome pair, per mitosis is in the normal distribution, while 14–100 exchanges is not normal and presents a danger to the organism. SCE is elevated in pathologies including Bloom syndrome, having recombination rates ~10–100 times above normal, depending on cell type.[1][2] Frequent SCEs may also be related to formation of tumors.
Sister chromatid exchange has also been observed more frequently in B51(+) Behçet's disease.[3]
^Ikbal M, Atasoy M, Pirim I, Aliagaoglu C, Karatay S, Erdem T (February 2006). "The alteration of sister chromatid exchange frequencies in Behçet's disease with and without HLA-B51". J Eur Acad Dermatol Venereol. 20 (2): 149–52. doi:10.1111/j.1468-3083.2006.01386.x. PMID16441621. S2CID28906261.