Chromosome folding. (A) Heat maps showing intrachromosomal contact frequencies for chromosome 4 obtained from conformation capture experiments (top left) (Duan et al. 2010), structure population (top right), random control (bottom left), and single chromosome population (bottom right). The latter is derived from a structure population for a nucleus containing only chromosome 4, constrained in a manner identical to the full simulation. Heat maps of the experiment and the structure population show characteristic folding patterns reminiscent of the back-folding of subcentromeric regions onto themselves. The heat maps of the random control and the single chromosome population lack the characteristic pattern. (B) Scheme showing the particular back-folding of the regions adjacent to both sides of the centromere for several chromosome configurations.
