Centromere Silencing

Through breakage-fusion-bridge or neocentromere formation a single chromosome may acquire more than one centromere. In a maize study, 6/23 chromosome derivatives of breakage-fusion-bridge cycle (between a B chromosome and chromosome 9) contained two centromere-specific regions (detected by immunolabeling) and were mitotically stable despite expectation according to the notion that dicentric chromosomes so derived would show bridge and breakage. This observation indicates that centromere inactivation may be common in plants (Han F et al 2006 Proc Natl Acad Sci USA 103:3238). B chromosomes, breakage-bridge-fusion cycles