Like a paint-by-numbers picture, painted probes tint individual human chromosomes by targeting specific DNA sequences. Chromosome 13 is colored green, chromosome 14 is in red and chromosome 15 is painted yellow. The image shows two examples of fused chromosomes - a pair of chromosomes 15 connected head-to-head (yellow dumbbell-shaped structure) and linked chromosomes 13 and 14 (green and red dumbbell). These fused chromosomes - called dicentric chromosomes - may cause fertility problems or other difficulties in people. A dicentric chromosome is an abnormal chromosome with two centromeres (the part of a chromosome that links sister chromatids or a dyad). It is formed through the fusion of two chromosome segments, each with a centromere, resulting in the loss of acentric fragments (lacking a centromere) and the formation of dicentric fragments.