I'm currently teaching some stuff on genome organisation, which includes
such things as introns early/late, mobile DNA (including self-splicing
A phenomemon that I can't seem to rationalise is the (relative)
confinement of mobile self-splicing introns to organelles. I appreciate
- they may have come into eukaryotes with organelles; BUT this hasn't
stopped loads of other organelle genes moving to the nucleus.
- they may have evolved into spliceosomal introns in the nucleus, as their
host organism would develop an interest in making damned sure that it
retained the machinery to splice them effectively out of coding regions.
BUT I don't see any reason why mobile self-splicing introns couldn't be
maintained in the longer term in nuclear genomes just as well as they have
been in many mitochondrial genomes.
- long-term maintenance of mobile elements in a genome usually requires
sex, so that elements can spread to unpopulated genomes. BUT this should
be even less of a barrier for nuclear mobile introns than for organelle
Thoughts on the back of an envelope, please, to
Dept of Genetics, University of Cambridge, Downing Street,
Cambridge CB2 3EH, UK
c.okane at gen.cam.ac.uk
Cahir O'Kane, Dept of Genetics, Univ. of Cambridge, UK
cok at mole.bio.cam.ac.uk