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It doesn't take that much to self-reproduce [message #83656] Mon, 10 June 2013 21:51 Go to next message
alexis is currently offline  alexis
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Message-ID: <696@reed.UUCP>
Date: Sun, 11-Nov-84 00:43:58 EST
Article-I.D.: reed.696
Posted: Sun Nov 11 00:43:58 1984
Date-Received: Tue, 13-Nov-84 00:43:39 EST
References: <241@hocsj.UUCP>
Organization: Reed College, Portland, Oregon
Lines: 50
Re: The missing step -- self-reproducing organisms


> That was my thinking up to this morning.  Now it strikes me that I have
> been glossing over a pretty complex step, one which is likely to have a
> lower probability than either of the ones mentioned above.  That is the
> step of going from something that is merely alive to a self-reproducing
> (SR) cell.  This, it seems to me, is the biggest step of the three.  It
> is one thing for the amino acids to form something that in some abstract
> sense is alive, it is quite another for this thing to be an SR organism.

    Actually, I think it is not a low-probability event at all.
Isolated DNA can self-replicate in the test tube. An organism would need
to feed itself in order to be (and stay) alive, wouldn't it? That means
assimilating matter from the outside. Thus it can also grow (by
assimilating more than it uses up). An incerase in size could cause a
primordial organism to fragment, much as a drop of oil will if shaken.
If there were enough copies of the genetic material in an organism
(and the restriction in the number of copies in higher organisms is no
doubt artificial) then all the pieces will probably get a full
complement of genetic material, QED. That is, a simple organism does not
need specialized structures for replicating.

    Of course, it sounds so simple because DNA does self-replicate.
That is probably why it is the "genetic material".

   The improbable event in the origination of life seems to be the
establishment of a functioning genetic code: The association of the DNA
with certain proteins that it "codes for", and which can "read" the
code, that is, produce the proteins coded for in the DNA.
(The process of transcription is enzyme-dependent, and enzymes are coded
for on the DNA).

   The improbable event is the origination of a self-maintaining
DNA-protein system. That may sound like what you had in mind to begin
with, but the production of molecules peculiar to an organism is a
fundamental part of being (and staying) "alive". I don't think I begged
the question.

    I should also mention that there is a difference between an event
like the origin of life and the evolution of intelligence. The origin of
life seems to have been a one-step, low-probability single event. (At
least, no one has come up with a multi-step mechanism for the crucial
part). Intelligence, on the other hand, is a product of evolution,
subject to the mechanisms of survival of the fittest etc. The one-step
origination of eyeballs would be hardly less improbable than the
one-step origin of intelligence.

                        Alexis Dimitriadis
                          alexis@reed

			  ...
Re: It doesn't take that much to self-reproduce [message #83661 is a reply to message #83656] Mon, 10 June 2013 21:51 Go to previous messageGo to next message
ericb is currently offline  ericb
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Message-ID: <2561@dartvax.UUCP>
Date: Mon, 12-Nov-84 21:35:26 EST
Article-I.D.: dartvax.2561
Posted: Mon Nov 12 21:35:26 1984
Date-Received: Tue, 13-Nov-84 06:56:48 EST
References: <241@hocsj.UUCP> <696@reed.UUCP>
Organization: Dartmouth College, Hanover, NH
Lines: 44

> 
> > That was my thinking up to this morning.  Now it strikes me that I have
> > been glossing over a pretty complex step, one which is likely to have a
> > lower probability than either of the ones mentioned above.  That is the
> > step of going from something that is merely alive to a self-reproducing
> > (SR) cell.  This, it seems to me, is the biggest step of the three.  It
> > is one thing for the amino acids to form something that in some abstract
> > sense is alive, it is quite another for this thing to be an SR organism.
> 
>    The improbable event in the origination of life seems to be the
> establishment of a functioning genetic code: The association of the DNA
> with certain proteins that it "codes for", and which can "read" the
> code, that is, produce the proteins coded for in the DNA.
> (The process of transcription is enzyme-dependent, and enzymes are coded
> for on the DNA).
> 
>    The improbable event is the origination of a self-maintaining
> DNA-protein system. That may sound like what you had in mind to begin
> with, but the production of molecules peculiar to an organism is a
> fundamental part of being (and staying) "alive". I don't think I begged
> the question.
> 
>                         Alexis Dimitriadis
>                           alexis@reed
> 
> 			  ...

The improbable event that Alexis mentions above is one of adding semantics
to a syntactic system.  This seems to me to be a *very* improbable event
because the mechanism for semantics (RNA transcription) is now coded for
in the DNA (excepting mitochondria).  In order to start at all, some original
standalone transcription system would have had to have been developed.  This
system (DNA & RNA transcription) would have existed in the cell without
benifiting the cell until some reasonable semantic code was arrived at.

This is where I would bet Nature spent three of the last four billion
years [overdue and overbudget!?! :-) ]

-- 
Eric Bivona
"Once a gene sequence, always a gene sequence"
UUCP:   ...!{astrovax, cornell, decvax, linus}!dartvax!ericb
CSNET:  ericb@dartmouth
ARPA:   ericb%dartmouth@csnet-relay
Re: It doesn't take that much to self-reproduce [message #89414 is a reply to message #83656] Mon, 24 June 2013 10:19 Go to previous messageGo to next message
davison is currently offline  davison
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Message-ID: <791@bnl.UUCP>
Date: Wed, 14-Nov-84 18:10:12 EST
Article-I.D.: bnl.791
Posted: Wed Nov 14 18:10:12 1984
Date-Received: Sat, 17-Nov-84 05:21:38 EST
References: <241@hocsj.UUCP> <696@reed.UUCP>
Lines: 77

> > That was my thinking up to this morning.  Now it strikes me that I have
> > been glossing over a pretty complex step, one which is likely to have a
> > lower probability than either of the ones mentioned above.  That is the
> > step of going from something that is merely alive to a self-reproducing
> > (SR) cell.  This, it seems to me, is the biggest step of the three.  It
> > is one thing for the amino acids to form something that in some abstract
> > sense is alive, it is quite another for this thing to be an SR organism.
> 
>     Actually, I think it is not a low-probability event at all.
> Isolated DNA can self-replicate in the test tube. An organism would need
> to feed itself in order to be (and stay) alive, wouldn't it? That means
> assimilating matter from the outside. Thus it can also grow (by
> assimilating more than it uses up). An incerase in size could cause a
> primordial organism to fragment, much as a drop of oil will if shaken.
> If there were enough copies of the genetic material in an organism
> (and the restriction in the number of copies in higher organisms is no
> doubt artificial) then all the pieces will probably get a full
> complement of genetic material, QED. That is, a simple organism does not
> need specialized structures for replicating.
> 
>     Of course, it sounds so simple because DNA does self-replicate.
> That is probably why it is the "genetic material".
> 
>    The improbable event in the origination of life seems to be the
> establishment of a functioning genetic code: The association of the DNA
> with certain proteins that it "codes for", and which can "read" the
> code, that is, produce the proteins coded for in the DNA.
> (The process of transcription is enzyme-dependent, and enzymes are coded
> for on the DNA).
> 
>    The improbable event is the origination of a self-maintaining
> DNA-protein system. That may sound like what you had in mind to begin
> with, but the production of molecules peculiar to an organism is a
> fundamental part of being (and staying) "alive". I don't think I begged
> the question.
> 
>     I should also mention that there is a difference between an event
> like the origin of life and the evolution of intelligence. The origin of
> life seems to have been a one-step, low-probability single event. (At
> least, no one has come up with a multi-step mechanism for the crucial
> part). Intelligence, on the other hand, is a product of evolution,
> subject to the mechanisms of survival of the fittest etc. The one-step
> origination of eyeballs would be hardly less improbable than the
> one-step origin of intelligence.
> 
>                         Alexis Dimitriadis
>                           alexis@reed
> 
> 			  ...




I would also suggest that those interested in the self-reproducing
organism problem look at the Scentific American article by Manfried
Eigen et al., April 1981.  He 
has done some interesting work and the hypercycle model, discussed
more coherently there than in other papers, has some interesting 
repercussions for chemical, self-reproducing "life" and evolution
of such "life"

(minor oxidation on)
Also, re the number of copies of the genetic material being limited
in higher animals, and artificial, no way.  Experiments done in Drospohila 
melanogaster (the fruit fly) since the time of T.H. Morgan (about 1920)
rather clearly demonstrate that having *extra* copies of some genes are very
detrimental to the organism, i.e. it dies or cannot reproduce, which
genetically is the same thing.  I think it would be safe to say 
that there are important constraints on the number of copies of genes.
especially those important in developmental regulation.
(minor oxidation off)
Dan Davison
Department of Microbiology
SUNY at Stony Brook
Stony Brook, NY 11794
arpa: davison@bnl
uucp: ..decvax!philabs!sbcs!bnl!davison
Re: It doesn't take that much to self-reproduce [message #89424 is a reply to message #83656] Mon, 24 June 2013 10:19 Go to previous message
lab is currently offline  lab
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Registered: February 2013
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Message-ID: <1546@qubix.UUCP>
Date: Mon, 19-Nov-84 14:25:29 EST
Article-I.D.: qubix.1546
Posted: Mon Nov 19 14:25:29 1984
Date-Received: Tue, 20-Nov-84 07:18:37 EST
References: <241@hocsj.UUCP> <696@reed.UUCP> <791@bnl.UUCP>
Organization: Quadratix ... Quartix
Lines: 22
Xref: sun net.bio:126 net.origins:520 net.philosophy:1167 net.sci:216 net.sf-lovers:4600

> Dan Davison:
> I would also suggest that those interested in the self-reproducing
> organism problem look at the Scentific American article by Manfried
> Eigen et al., April 1981.  He 
> has done some interesting work and the hypercycle model, discussed
> more coherently there than in other papers, has some interesting 
> repercussions for chemical, self-reproducing "life" and evolution
> of such "life"

If Eigen's hypotheses are the same as those in _Das Spiel_, Wilder
Smith's book deals with them in depth.

Aside to John Woods: What was it that AEWS said that MIT Freshlings
supposedly know better of? The people at the U of Illinois Medical
center (where, as a professor of pharmacology, he continually received
awards for best series/course of lectures) might like to know. Then
again, freshmen often think they know everything.
-- 
		The Ice Floe of Larry Bickford
		{amd,decwrl,sun,idi,ittvax}!qubix!lab

You can't settle the issue until you've settled how to settle the issue.
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