[LMB] (Slightly) OT: Mitochondria (No spoilers) back on topic

[Tora K. Smulders-Srinivasan]

> The Sundance Kid wrote:
> > Am I the only one who sees "Mitochondrial" and, when reading quickly, flashes to power converters, blue milk and wondering who shot first?

On 7/18/07, Elvi Dalgaard <elvi at vl.videotron.ca> wrote:
> >
> Not sure, but for me it's all L'Engle, all the time. Totally Wrinkle in
> Time, since that's where I learned the word in the first place.

Hunh?  I don't get Sundance Kid's reference.  I do get Elvi's, but I'm
afraid since I work on mitochondrial disease, the word flashes me back
to work.  :-(  So let's not talk about mitochondria anymore, 'kay?
;-)  Just kidding.

Though, I gotta say, mitochondrial inheritance is a very very unlikely
manner of actually passing on genes.  There are exactly 13
polypeptides encoded by the mitochondrial genome (1 polypeptide = one
part of a completed protein, though some proteins are made up of only
one) and all of them are essential parts of mitochondrial machinery.
As is anything else encoded by the mitochondria.  So it's highly
unlikely that a gene for groundsense would be slopped into the
mitochondrial genome -- it's a tiny piece of DNA (only ~1.6 kb) and
very highly selected and very stripped down and without lots of junk
DNA as you get in the nuclear genome.

On the other hand, if you're using the term mitochondrial inheritance
as a shorthand for inherited only through the mother, that's
different.  You could even have it be another organelle with its own
DNA (mitochondria are unique in that in human (& all animal) cells,
but photosynthesizing plants also have chloroplasts that have their
own genome), that is inherited similarly, but is specific to
groundsense.

Honestly, though, I think the easiest explanation would be something
that's in the nuclear DNA but multigenic, with some genes that are
very important to the trait and a bunch of modifier genes, spread
across a bunch of different chromosomes.  This is a pretty common
problem in genetics -- pure dominant/recessive single gene traits are
very rare, and the multigenic thing makes the whole inheritance thing
complicated to the point of us not being able to figure it out.  Which
would mean the TSK people wouldn't be able to if it hit them on the
head -- considering their biological knowledge seems fairly basic.

Thus, they'd just have complicated inheritance.  Mostly, breeding
those that show the trait will give you offspring that have, but you
may not always get that.  Also, if some of the people that were left
out of the Lakewalker breeding scheme had some of the genes, but the
individuals didn't actually have strong groundsense -- they'd have
been thrown into the Farmers pool.  And in the generations since, some
of the genes may have been brought together randomly and combined in
some of the lineages to the point where some of the Farmers may
actually have groundsense.  If they came into their "power" in their
teens and had no training, it could easily manifest as something adult
would take as an example of an especially "difficult" teenager.

Plus, don't underestimate the power of taboo and the need for
teenagers to conform.  Lakewalker "magic" is something that Farmers
are scared of and abominate as something evil -- they use dead bodies
and all.  So a teenager with something even stranger going on than
normal wouldn't necessarily get a comforting reception from adults.
And being a teenager looking for conformity, would be most likely to
hide and possibly actively suppress whatever strangenesses he/she
might find inside him/herself.  The analogy with discovery of
"taboo" sexual preferences as teenagers is hard to deny here.

Yikes, didn't mean to yammer on.  But I have been wanting to say
something about the genetic speculation going on about groundsense
(being a geneticist, how could I not?) and I suppose The Sundance Kid
and Elvi triggered it!  ;-)

-Tora