Furthermore, the unusual architecture of the rod nuclei provides new insights into the early evolution of mammals. This special arrangement of genetic material must have originated more than a hundred million years ago when the ancestors of today's mammals adopted a nocturnal lifestyle to avoid the dominant carnivorous reptiles of the time. Their nocturnal descendants have preserved the inverted rod nuclear architecture to this day, but those descendants that have later become diurnal - including us humans - have reverted to the conventional rod nuclear organisation. "This confirms the superiority of the conventional architecture", says Joffe. "Obviously, the inverted nuclear organisation also has - as yet unknown - disadvantages".
A possible advantage of the conventional architecture is that the central positioning of the active eurochromatin allows more interactions between neighbouring gene loci and with the transcription apparatus in three dimensions; euchromatin in a peripheral shell factually has only two dimensions for contacts. However, in nocturnal mammals the advantages of improved night vision seem to have prevailed.
|Contact: Dr. Leo Peichl|