DCJ-DS model. The four chromosomal fragments produced by a pair of cuts on different chromosomes can be rejoined in two ways. Inter-chromosomal rearrangement that would change the chromosomal-scale connectivity of sensitive genes (x’s) are rejected. Rearrangements are accepted only when one side of each breakpoint is free of sensitive genes both before and after the move. A: Illegal cuts. Connectivity of sensitive genes would be broken in any of these moves. B: Illegal rejoins. Sensitive genes from different chromosomes would be rejoined (or split) in the rejected moves.