Figure 1.

BFB cycles. (A) Ring chromosomes that have undergone a sister chromatid exchange or a torsion may form bridges at anaphase that subsequently break and rejoin into new rings. As bridges may break at any point between the centromeres, the rings in the daughter cells can be different from each other and from the ring in the mother cell. (B) Dicentric chromosomes and chromosomes involved in telomeric associations can also form bridges at anaphase. The broken ends may rejoin subsequently or rearrange with other broken chromosomes, forming new variants of dicentric chromosomes.