Physical linkages between sister chromatids and their removal during yeast chromosome segregation.

The fidelity of chromosome inheritance is of paramount importance to all living organisms. In eukaryotic cells, the strategy to ensure physical segregation of chromosomes to daughter cells relies on two basic steps ordered in time: an initial linkage, or cohesion, of sister chromatids and its timely and complete dissolution during anaphase. The current view is that these two basic steps are accomplished around the regulation of a protein complex called cohesin that serves as "clamp brackets" distributed at intervals throughout the genome. However, many of the DNA metabolic activities during interphase also produce physical linking of chromatids. For example, during replication, intertwines between sister chromatids are formed. Here, we review our understanding of the processes that generate physical linkages between chromatids and discuss potential mechanisms that are involved in the removal of such obstacles to the complete physical separation of chromatids at anaphase.