Re: Chromosome rearrangements in mammals


"Perplexed in Peoria" <jimmenegay@xxxxxxxxxxxxx> wrote in message
news:drds5k$27ks$1@xxxxxxxxxxxxxxxxxxxxxx

<SNIPPING DONE ONLY FOR SAKE OF SPACE>
Muchas gracias. Muchisimas!

> Most interchromosomal rearrangements are the result of accidental
> crossing-over between homologous segments on nonhomologous
> chromosomes, and these events are often promoted by chromosomal
> inversion within one of the segments.

(Interrupting your paragraph to speak to this issue...) One of the things
that has been knocking at the door of my thoughts on the matter of
homologous comparative interspecies chromosomal arrangements is whether
there just MIGHT ever have been any OTHER ways -- other than reproductive
errors at some loci, on the one hand, along with reproductive accuracies, on
others, from generation to generation --whereby snippets of sequences may
have crossed over between one complex co-contemporary species and another.

Let me assure you that I am aware... that if non-heritable cross-overs
between species had occurred to any substantial extent over these past
millions of years of bio-evo, there could not be today any tree-like
patterns to suggest the kinds of typological formats various biologists have
come up with (regardless the amount of controversy that has arisen and is
arising as to where some of the pieces of those trees actually belong).
Hence, it seems very likely that IF any co-contemporary species cross-overs
of snippets has occurred, they have been quite rare. (Yet might, also,
serve to explain some of the apparent contradictions typologists have in
reconciling to a single, mutually perceived evolutionary "tree.")

Let me assure you, also, that I am aware... there are many obstacles that
have been run into, so far, by researchers who are trying to tease out the
details of how and why various incompatibilities stand in the way of
attempts to "fix" the DNA of individuals that have some of the "simpler"
genetically-based pathologies by altering . Within my limited familiarity,
I discern that some of these obstacles that have been run into are
attributable to immune and/or auto-immune mechanisms, while others, if I've
got it right, have to do with what might be comparable to veritable
"programming incompatibilities." The immune system has been under intensive
and extensive scrutiny and manipulation techniques for many years. What may
be "programming incompatibilities," on the other hand, would only be as
decipherable as the level of our understanding in fine detail of how genes,
enzymes, proteins, traits... actually relate to one another. And --
although new data is flowing in on these fine details -- my impression is
that this data comes from many and various different research specialties
and may take a long time to be related into syntheses even after much raw
data has been accumulated.

But here is something very important, I think, for us to understand, lest we
toss out any notion of an occasional exception to the veritable "firewall"
of barriers a genome of an individual poses against being corrupted. Nature
sometimes DOES, over evolutionarily significant periods of time, achieve
some otherwise unlikely accomplishments (not the least being the origin of
life, itself). But, even if a tortuously unlikely, but serendipitous, way
had occurred -- even by one chance in a million, for some exchange medium,
such as, say, a bacteria in the proboscis of a mosquito to take in a snippet
of DNA from one organism that could get past all the veritable check points
and succeed in EDITING the genome of one individual, it would seem to me
this very same vector most likely would be unsuccessful in editing the DNA
of any other individual, much less many of another species.

Case in point: In human organ transplant protocols, even where a "good"
match is found, between donor and recipient, both defense-type (immune and
auto-immune) responses can be triggered (is this not the general rule,
rather than the exception???). But the role played by what might be
equivalent to interstitial "programming incompatibilities" would seem
likely. By that I mean that it is one thing to view the DNA of subject
organism A as working, as is, for A, and the DNA of subject B as working, as
is, for B. But if some chromosome of A were to be inserted into B, to EDIT
B, what are the chances that the AB combination would present "programming
incompatibilities" DURING THE TIME OF THE PROCESS OF Bs CONVERSION?
(This question is not as simple as blood-type compatibilities versus
incompatibilities. After all, if there are any other factors than RH ones
in instances of transfusion, the recipient's body's entire DNA does not
become edited by them but, if I understand correctly, attacks and destroys
what it discerns to be foreign and merely utilizes what remains (of course
perhaps picking up a few viruses or vegetables or animals it may or may not
be harmed by).

Please understand that I am not arguing a case for maintaining that
inter-species crossovers at the post-natal portions of life cycles of two
co-contemporary organisms from two species HAVE occurred, or even COULD
occur. I only am wondering whether, and if so how, and if so what if... I
would not even recommend (necessarily) that any research be conducted with
finding out as its goal. I WOULD submit that specific FACETS of the
question can be, should be, and are being... conducted, however, and that if
data from THOSE various sources SHOULD happen to converge upon a possibility
that it has, or could, occur... then the full spectral width of that
convergence would be interesting. The details whereby such convergence
might be derived, however, would be far more important in their applications
to specific
goals of medical science. And, what is more, even if all the details (known
and as yet undetermined) were to converge in such a way as to rule out even
the remotest chance that any crossover of DNA from one to another of two
adult co-contemporary organisms of two species were impossible, the details
leading up to that would nonetheless be -- just as useful in guiding how
medical science could use that information in setting up ways to make it
happen (i.e., to successfully modify the DNA of a patient with a
genetically-based pathology).

But, as I have reflected on so many times, knowledge is (in the Hobbesian
sense) a form of power; and any and all power can be utilized for good or
for evil.

Determinations of the details is pouring in. Much of it, already in, has
not been in long enough for syntheses to have been pulled together with
which to form new conceptual models to integrated them. They keep pouring
in, regardless.

What a marvelous time to be alive. And how sobering it is to contemplate
that, for each and all of us,
the curtain will not come down. We shall simply leave the theater, and none
of us now enjoying it be around for the final act... hopefully.

That being the case, I thoroughly have enjoyed this article's review by
PiP, the last paragraph of which reads:

>It is not clear why some
> of these rearrangements and not others have become fixed in evolution
> and why some are prone to further evolutionary rearrangement. The
> answers to these questions may be found in the comparative study
> of additional species using the analysis of sequence data of the
> type initiated by the authors of this interesting study.

Thanks again. And... how sweet it is...


g



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