Re: Fw: Most popular/common dinosaur misconceptions

[Roberto Takata <rmtakata@gmail.com>]

On 8/24/06, David Marjanovic <david.marjanovic@gmx.at> wrote:
> > remember that most of proteome present in the mitochondria are of
> > nuclear origin, which could imply a early gene transfer from
> > mitochondria (or the original endossymbiont) to nucleus.
>
> Certainly -- these must have happened before animal mitochondria started
> evolving their own code.

Or maybe not. (Say, Ryckettsia has a non-standard genetic code.
Wolbachia has a non-standard code too - and there is registered gene
transfer to host.)

> > How could genetic system with different genetic code be compatible?
> > First, it could be the case that the translation system was not so
> > specific or so reliable. Recall the wobble hypothesis of codon origin.
>
> If the codes are too different, this still won't work.

Maybe they are not *too* different at that time - dozens of million of
years of previous coexhistence could have led to a high degree of
convergent coevolution and there is the stereochemical hypothesis for
the genetic code origin too.

> > And, on the other hand, termination codon is not a yes or no codon,
> > but a probabilistic codon - which depend somewhat of the genetic
> > context (the flanking sequences).
>
> Are you talking about selenocystein?

No, I'm refferring to the low efficiency oy Trp coding by UGA
(standard stop codon) in _Bacillus subtilis_ and in _Escherichia
coli_.

Hatfield D, Diamond A. 1993 - UGA: a split personality in the
universal genetic code. Trends Genet. 9(3): 69-70

[]s,

Roberto Takata