Figure 2.

Segregation errors observed upon topoisomerase II malfunction. Impairment of topoisomerase II function results in lack of sister chromatid resolution and insufficiently compacted chromatin. In normal mitosis, sister chromatid intertwines are almost fully resolved at metaphase to ensure faithful genome segregation. Lack of topoisomerase II results in extensive entanglements between sister chromatids that persist during anaphase. Such entangled DNA threads not only hinder equal chromosome segregation, but may also lead to generation of breaks in DNA. In addition, chromosomes deprived of topoisomerase II display lowered levels of compaction. Under-compacted chromosomes are also prone to segregation errors during anaphase and cytokinesis, as the cleavage furrow may trap long and missegregated chromatids.