Mitotic chromosome dimensions differ between species, and they differ between developmental stages within an organism. The physiological determinants of chromosome size remain poorly understood. Here, we investigate chromosome size determinants in the fission yeast Schizosaccharomyces pombe. Super-resolution microscopy and semi-automated measurements reveal that cell or nuclear volume in interphase, or the time spent in mitosis (both previously proposed chromosome size determinants), have little influence on resultant chromosome dimensions. Instead, levels of the chromosomal condensin complex affect chromosome size, with increasing condensin levels resulting in more compact, thinner and shorter, chromosomes. Our observations inform the understanding of how chromosome dimensions are controlled in an organism. They suggest that a chromosome-intrinsic mechanism sets chromosome size, more so than the environment in which chromosomes find themselves in.
Wu et al. (Wed,) studied this question.