Dicentric chromosome

Dicentric chromosome is an aberrant chromosome having two centromeres. Dicentric chromosomes form when two chromosome segments (from different chromosomes or from the two chromatids of a single one), each with a centromere, fuse end to end, with loss of their acentric fragments. Dicentrics, despite their two centromeres, may be mitotically stable if one of the two centromeres is inactivated, or if the two centromeres always coordinate their movement to one or the other pole during anaphase. Such chromosomes are formally called pseudodicentric. The most common pseudodicentrics involve the sex chromosomes or the acrocentric chromosomes (Robertsonian translocation). Evaluation of centromere function by FISH combined with immunofluorescence analysis of centromere and kinetochore proteins is a specialized procedure in some clinical cytogenetics laboratories.

As telomeres shorten with continued cell divisions, the chromosome-ends fuse forming dicentric chromosomes. This is considered "Crisis" or M2. Most cells in M2 will suffer apotosis.