Modelling and simulation of polycomb-dependent chromosomal interactions in drosophila

Abstract

The conditions of the chromosomes inside the nucleus in the Rabl configuration have been modelled as self-avoiding polymer chains under restraining conditions. To ensure that the chromosomes remain stretched out and lined up, we fixed their end points to two opposing walls. The numbers of segments $N$, the distances $d_1$ and $d_2$ between the fixpoints, and the wall-to-wall distance $z$ (as measured in segment lengths) determine an approximate value for the Kuhn segment length $k_l$. We have simulated the movement of the chromosomes using molecular dynamics to obtain the expected distance distribution between the genetic loci in the absence of further attractive or repulsive forces. A comparison to biological experiments on \textit{Drosophila Melanogaster} yields information on the parameters for our model. With the correct parameters it is possible to draw conclusions on the strength and range of the attraction that leads to pairing.