[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
RE: Tuataras are the roadrunners of molecular evolution.
David Marjanovic wrote:
>> On the other hand, what would hyper-variable mitochondrial control regions
>> have to do with rate of morphological (or indeed physiological) evolution?
> As far as I can tell, nothing whatsoever...
Yep, nothing at all. The mitochondrial control region is involved in the
replication of the mitochondrial genome (especially the 'heavy-strand', on
which most of the mitochondrial proteins are encoded), and in the transcription
of those genes carried on the mitochondrial genome. Nobody is exactly sure how
the control region does all this, although certain individual sequences within
this region appear to be implicated (somehow).
The thing is, it is possible that animals with a 'slow' metabolism (like the
tuatara) may be better able to tolerate mutations that have a deleterious
effect on the performance of the control region. If mutations accumulate to
such a degree that it reduces the efficacy of mitochondrial replication and/or
transcription, then it may not matter to an animal with a slow metabolism.
Mitochondria are regarded as little 'power plants' for the cell, and rapid
replication and transcription of the mitochondrial genome is considered
important for overall aerobic efficiency (which is why the mitochondrial genome
tends to be very small and compact). However, animals with a slow metabolism
may have an increased tolerance for reduced aerobic efficiency; it makes no
difference to their physiology if the mitochondria are less efficient at
producing energy. Thus, these animals may have a higher tolerance for the
accumulation of mutations within the control region. Changes in the control
that are effectively neutral to the tuatara, may not be neutral to an organism
with a fast metabolism (like us humans!), and which is dependent on the optimal
aerobic efficiency of its mitochondria.
Long story short... the high rate of molecular change in the tuatara control
region may be a *consequence* of a slow metabolism.
Shed those extra pounds with MSN and The Biggest Loser!