(2017-12-06, 05:41 PM)DaveB Wrote: [ -> ]Well I think left and right in politics have become rather confused in recent years, but I'll tell you straight out, I would have voted Trump in the last election if I was American. I think Hillary might have started a war with Russia over Syria. In the past, the left were very much in favour of peace, but that doesn't seem to be true any more.
Yikes.
And Hillary is not "the left."
~~ Paul
(2017-12-06, 05:45 PM)DaveB Wrote: [ -> ]But surely it would do something - because for example
C A T T G G
would be read as CA TT GG by a 2-base reader
and as
CAT TGG by a 3-base reader
How can the organism's genome survive that change?
Oh sorry, yes, the change would have to happen before there was much in the way of stored genes. It could have happened when short peptides were being assembled at random.
We don't know the story yet (if ever). But it's important not to picture the sequence as:
nothing at all . . . poof! . . . the current system
Here, for example, is a proposal that two doublet codes were read by a triplet reader:
https://www.ncbi.nlm.nih.gov/pubmed/16059752
~~ Paul
(2017-12-06, 07:08 PM)Paul C. Anagnostopoulos Wrote: [ -> ]Oh sorry, yes, the change would have to happen before there was much in the way of stored genes. It could have happened when short peptides were being assembled at random.
Right - so we get right down to it - everything is done by random processes unguided even by natural selection - which is basically why I think that the existence of the genetic code is pretty solid evidence for ID or something of that nature. It could of course be aliens if you like, inventing a better form of life and seeding the earth with the stuff, but a 3-base code can't possibly evolve from a 2-base code because the code is needed to specify all sorts of little details little details like ribosomes!
David
(2017-12-06, 09:12 PM)DaveB Wrote: [ -> ]Right - so we get right down to it - everything is done by random processes unguided even by natural selection - which is basically why I think that the existence of the genetic code is pretty solid evidence for ID or something of that nature. It could of course be aliens if you like, inventing a better form of life and seeding the earth with the stuff, but a 3-base code can't possibly evolve from a 2-base code because the code is needed to specify all sorts of little details little details like ribosomes!
David
Natural Selection is more accurately defined as adaptation do to external variables. For example rats living in uptown Manhattan vs. rats living in downtown Manhattan.
Quote:Study shows genetic differences between uptown and downtown rats living in Manhattan
(Phys.org)—A small team of researchers from Fordham University and Providence College, both in the U.S., has found that there are small but discernible genetic differences between rats living uptown versus downtown on the island of Manhattan. In their paper published in the journal Molecular Ecology, the group describes trapping rats from one end of the island to the other, conducting genetic tests on them and outlining what they found.
Read more at: https://phys.org/news/2017-12-genetic-di...s.html#jCp
[url=https://phys.org/news/2017-12-genetic-differences-uptown-downtown-rats.html#jCp][/url]
New theory addresses how life on Earth arose from the primordial muck
Life on Earth originated in an intimate partnership between the nucleic acids (genetic instructions for all organisms) and small proteins called peptides, according to two new papers from biochemists and biologists at the University of North Carolina at Chapel Hill and the University of Auckland. Their "peptide-RNA" hypothesis contradicts the widely-held "RNA-world" hypothesis, which states that life originated from nucleic acids and only later evolved to include proteins.
The new papers - one in
Molecular Biology and Evolution, the other in Biosystems - show how recent experimental studies of two enzyme superfamilies surmount the tough theoretical questions about how complex life emerged on Earth more than four billion years ago.
"Until now, it has been thought to be impossible to conduct experiments to penetrate the origins of genetics," said co-author Charles Carter, PhD, professor of biochemistry and biophysics at the UNC School of Medicine. "But we have now shown that experimental results mesh beautifully with the 'peptide-RNA' theory, and so these experiments provide quite compelling answers to what happened at the beginning of life on Earth."
Read more at:
https://phys.org/news/2017-11-theory-lif...l.html#jCp
I'm also having trouble understanding the argument for origin of life from the point of view of probability.
This is from
Evolution FAQ:
Quote:In fact, if we assume the volume of the oceans were 1024 liters, and the amino acid concentration was 10-6M (which is actually very dilute), then almost 1031 self-replicating peptides would form in under a year, let alone millions of years. So, even given the difficult chances of 1 in 1040, the first stages of abiogenesis could have started very quickly indeed.
And this from
Talk Origins:
Quote:Similarly, of the 1 x 10130 possible 100 unit proteins, 3.8 x 1061 represent cytochrome C alone! There's lots of functional enyzmes in the peptide/nucleotide search space, so it would seem likely that a functioning ensemble of enzymes could be brewed up in an early Earth's prebiotic soup.
So, even with more realistic (if somewhat mind beggaring) figures, random assemblage of amino acids into "life-supporting" systems (whether you go for protein enzyme based hypercycles , RNA world systems, or RNA ribozyme-protein enzyme coevolution) would seem to be entirely feasible, even with pessimistic figures for the original monomer concentrations [23] and synthesis times.
Yet, unless I'm mistaken, life has originated only once in 4.5 billion years of planetary history. If it is so likely as to be "entirely feasible", why then has it not happened multiple times? Crick calls it a "frozen accident" indicating its uniqueness and unlikeliness. So my mind got to wondering whether, if some blast of radiation from the sun obliterated all life from this planet yet allowed the earth to return quickly to its life-friendly status, are we assuming that another frozen accident would occur quickly? And, if so, would that be another one-off?
The point I'm trying to make is that the arguments seem to be self contradicting.
(2017-12-06, 09:12 PM)DaveB Wrote: [ -> ]Right - so we get right down to it - everything is done by random processes unguided even by natural selection
Hang on. The peptides are generated at random, but some are useful and some are not. So the chemical processes that produce the useful ones remain and the other processes disappear. So over time, various processes stick around.
Sorry, I didn't mean to suggest that the processes are completely uniformly random. That is confusing. There would be various chemical processes, some producing useful products and some not. There would have to be some way to "hang onto" the useful ones and ignore the useless ones. That rudimentary system is subject to natural selection.
The question is, how does the system hang onto the useful products? Check out the next post for one possibility.
Quote:... but a 3-base code can't possibly evolve from a 2-base code because the code is needed to specify all sorts of little details little details like ribosomes!
Who says there were modern ribosomes when the 3-base code evolved? Perhaps there was a proto-ribosome that stepped along the RNA by 3 bases but paid attention to only 2 of them. Again, see the next post.
~~ Paul
(2017-12-06, 11:56 PM)Steve001 Wrote: [ -> ]New theory addresses how life on Earth arose from the primordial muck
Life on Earth originated in an intimate partnership between the nucleic acids (genetic instructions for all organisms) and small proteins called peptides, according to two new papers from biochemists and biologists at the University of North Carolina at Chapel Hill and the University of Auckland. Their "peptide-RNA" hypothesis contradicts the widely-held "RNA-world" hypothesis, which states that life originated from nucleic acids and only later evolved to include proteins.
The new papers - one in Molecular Biology and Evolution, the other in Biosystems - show how recent experimental studies of two enzyme superfamilies surmount the tough theoretical questions about how complex life emerged on Earth more than four billion years ago.
"Until now, it has been thought to be impossible to conduct experiments to penetrate the origins of genetics," said co-author Charles Carter, PhD, professor of biochemistry and biophysics at the UNC School of Medicine. "But we have now shown that experimental results mesh beautifully with the 'peptide-RNA' theory, and so these experiments provide quite compelling answers to what happened at the beginning of life on Earth."
Ooh, those will be fascinating papers. They propose a protein-RNA world.
https://academic.oup.com/mbe/advance-art...65/4430325
http://www.sciencedirect.com/science/art...4717302332
~~ Paul
Kamarling Wrote:Yet, unless I'm mistaken, life has originated only once in 4.5 billion years of planetary history. If it is so likely as to be "entirely feasible", why then has it not happened multiple times? Crick calls it a "frozen accident" indicating its uniqueness and unlikeliness. So my mind got to wondering whether, if some blast of radiation from the sun obliterated all life from this planet yet allowed the earth to return quickly to its life-friendly status, are we assuming that another frozen accident would occur quickly? And, if so, would that be another one-off?
First, of course, we don't know how many times life started on the primordial Earth. I can think of two reasons why it wouldn't start up again today: (1) the conditions aren't right; (2) there is too much competition from current life.
If we reset the Earth to its primordial conditions, I see no reason life wouldn't start again. It might come out the same or it might not. I believe the two papers Steve linked will suggest that it would come out more or less the same.
~~ Paul