“…None of these features cannot be produced by indiscriminate cross-linking of chromosomes ( Marko and Siggia, 1997 ), which suggests that a novel mechanism of polymer compaction must occur, namely 'lengthwise compaction' ( Marko, 2009 ; 2011 ; Marko and Rippe, 2011 ), which permits each chromatid to be compacted while avoiding sticking of separate chromatids together. Cell-biological studies suggest that topoisomerase II and condensin are essential for metaphase chromosome compaction ( Hirano and Mitchison, 1993 ; 1994 ; Wood and Earnshaw, 1990 ; Hirano, 1995 ), leading to the hypothesis that mitotic compaction-segregation relies on the interplay between the activities of these two protein complexes.…”