Unraveling mitotic chromosome structure using optical tweezers

Abstract

During mitosis, vertebrate chromosomes compact into X-shapes that are approximately four orders of magnitude shorter than the contour length of the DNA-molecules they consist of. Visualizing the internal structure of these mitotic chromosomes is difficult because of their high compaction, though some light has been shed on this problem using electron microscopy, (superresolution) fluorescence microscopy and Hi-C experiments. Currently, the leading hypothesis is that chromatin is ordered in loops that emanate from a central scaffold, and that are formed by protein complexes Condensin I and Condensin II by the process of loop-extrusion.