Condensin and cohesin are two such complexes that act on chromosomes to facilitate their higher-order organization.

The solution to dealing with an extremely viscous environment is to use energy-dependent machines to speed up DNA metabolic processes. The consequence of such a high effective viscosity is that the rate of entropic fluctuations on the chromosome will be excruciatingly slow. This effective viscosity includes both molecular crowding and myriad short-lived interactions the chromosome encounters upon recoil to a random coil. They estimated the intracellular viscosity on the order of 141 poise or 14,100-fold higher than water. In that work, the recoil of a broken dicentric chromosome was visualized following DNA breakage in anaphase. 2009) made estimates on the nature of the cellular environment from the perspective of the chromosome. The use of small molecules to estimate viscosity inform us more about the interstitial water in the nucleoplasm than the viscosity affecting an entire chromosome. In contrast, simulating the physical properties of the cellular environment has proven more difficult. The use of bead-spring models to simulate the behavior of the chain have proven to be highly valuable. Understanding how biochemical reactions influence chromosome organization requires that we account for the large conformational fluctuations of the DNA itself. Loops spontaneously form as chromatin collides and wriggles about itself. Entropic penalties prevent chromosome intermixing, hence most of the interactions are intra-chromosomal loops. Confining this long-chain polymer in the nucleus produces intra-chain interactions, otherwise known as loops. Thermal fluctuations dominate the spatial organization of chromosomes while active kinetic processes modulate this organization. Studying DNA from the perspective of a long-chain polymer has enabled tremendous strides in understanding genome organization.

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