Inside each of the hundred million million (or so) cells in your body there is a nucleus which holds the cell's DNA. All of that DNA, if stretched out, would reach to the moon and back many thousands of times. But in the nucleus it is cleverly arranged and compacted to fit in such a small space. Of course the genes that are being used in any given cell are not so compacted. Now, new research is telling us more about how the DNA is arranged in the nucleus.
The new findings reveal that typically the silent and compacted DNA regions sit along the outer edges of the nucleus while the active and less compacted genes cluster around the the center of the nucleus.
In a fascinating exception to this pattern, the arrangement is reversed in the nucleus' of retina cells of nocturnal mice. The compacted, silent, DNA resides at the nucleus center while the less compacted, active, DNA is in the outer regions. This same pattern was found in 38 such species. These species see better in low light conditions, and presumably this rearrangement helps achieve that capability.
Of course such DNA arrangements are highly complex, and changing the arrangement is unlikely to be achieved by a single mutation.
How curious it is that such complexities and interdependencies are so often found in biology.