yeast, and the chicken DT40 cells. The outcome of these studies strongly supports the notion that condensins play crucial roles in mitotic chromosome assembly and that condensin I and II have distinct functions in this process. Moreover, quantitative imaging analyses allow researchers to count the number of condensin complexes present on human metaphase chromosomes. Meiosis Condensins also play important roles in chromosome assembly and segregation in meiosis. Genetic studies have been reported in S. cerevisiae, D. melanogaster, and C. elegans. In mice, requirements for condensin subunits in meiosis have been addressed by antibody-mediated blocking experiments and conditional gene knockout analyses. In mammalian meiosis I, the functional contribution of condensin II appears bigger than that of condensin I. As has been shown in mitosis, however, the two condensin complexes have both overlapping and non-overlapping functions, too, in meiosis. Unlike cohesin, no meiosis-specific subunits of condensins have been identified so far. Chromosomal functions outside of mitosis or meiosis Recent studies have shown that condensins participate in a wide variety of chromosome functions outside of mitosis or meiosis. In budding yeast, condensin I (the sole condensin in this organism) is involved in copy number regulation of the rDNA repeat as well as in clustering of the tRNA genes. In fission yeast, condensin I is involved in the regulation of replicative checkpoint and clustering of genes transcribed by RNA polymerase III. In C. elegans, a third condensin complex (condensin IDC) related to condensin I regulates higher-order structure of X chromosomes as a major regulator of dosage compensation. In D. melanogaster, condensin II subunits contribute to the dissolution of polytene chromosomes and the formation of chromosome territories in ovarian nurse cells. Evidence is available that they negatively regulate transvection in diploid cells. It has also been reported that condensin I components are required to ensure correct gene expression in neurons following cell-cycle exit. In A. thaliana, condensin II is essential for tolerance of excess boron stress, possibly by alleviating DNA damage. In mammalian cells, it is likely that condensin II is involved in the regulation of interphase chromosome architecture and function. For instance, in human cells, condensin II participates in the initiation of sister chromatid resolution during S phase, long time before mitotic prophase when sister chromatids become cytologically visible. In mouse interphase nuclei, pericentromeric heterochromatin on different chromosomes associates with each other, forming a large structure known as chromocenters. Cells deficient in condensin II,