Recent experiments showing scaling of the intrachromosomal contact probability, P(s)\sim s^{-1} with the genomic distance s, are interpreted to mean a self-similar fractal-like URLanization. However, scaling of P(s) varies URLanisms, requiring an explanation. We illustrate that dynamical arrest in a highly confined space as a discriminating marker for URLanization, by modeling chromosome inside a nucleus as a self-avoiding homopolymer confined to a sphere of varying sizes. Brownian dynamics simulations show that the chain dynamics slows down as the polymer volume fraction (\phi) inside the confinement approaches a critical value \phi_c. Using finite size scaling analysis, we determine \phi_c^{\infty}\approx 0.44 for a sufficiently long polymer (N\gg 1)  . Our study shows that the onset of glassy dynamics is the reason for the formation of URLanization in human chromosomes (N\approx 3\times 10^9, \phi\gtrsim\phi_c^{\infty}), whereas chromosomes of budding yeast (N\approx 1.2\times 10 ^7 , \phi<\phi_c^{\infty}) are equilibrated with no clear signature of URLanization.
Recent experiments showing scaling of the intrachromosomal contact probability, P(s)\sim s^{-1} with the genomic distance s, are interpreted to mean a self-similar fractal-like URLanization. However, scaling of P(s) varies URLanisms, requiring an explanation. We illustrate dynamical arrest in a highly confined space as a discriminating marker for URLanization, by modeling chromosome inside a nucleus as a homopolymer confined to a sphere of varying sizes. Brownian dynamics simulations show that the chain dynamics slows down as the polymer volume fraction (\phi) inside the confinement approaches a critical value \phi_c. The universal value of \phi_c^{\infty}\approx 0.44 for a sufficiently long polymer (N\gg 1) allows us to discuss genome dynamics using \phi as a single parameter . Our study shows that the onset of glassy dynamics is the reason for the segregated URLanization in human (N\approx 3\times 10^9, \phi\gtrsim\phi_c^{\infty}), whereas chromosomes of budding yeast (N\approx 10 ^8 , \phi<\phi_c^{\infty}) are equilibrated with no clear signature of URLanization.
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that
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self-avoiding
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Using finite size scaling analysis, we determine
The universal value of
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allows us to discuss genome dynamics using \phi as a single parameter
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formation of
segregated
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chromosomes
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1.2\times
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^7
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