Before revision:  We present a simple biophysical model , where chromosomes are described in terms of folding of a chromatin sequence with alternating blocks of fibers with different thickness. We demonstrate that chromosomes undergo prominent conformational changes when the two fibers form separate domains.
After revision:  We present a simple biophysical model , where chromosomes are described in terms of folding of a chromatin sequence with alternating blocks of fibers with different thicknesses and flexibilities, and we use it to study the influence of sequence disorder on chromosome behaviors in space and time. By employing extensive computer simulations,we thus demonstrate that chromosomes undergo prominent conformational changes when the two fibers form separate domains.