The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes"
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I can't easily digest with my primitive understanding of genetics.
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
On Wednesday, November 3, 2021 at 10:10:51 PM UTC-7, erik simpson wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes """Even more astonishingly, they were the same as the tiny chromosomes of Amphioxus – a little fish-like animal with no backbone that last shared a common ancestor with vertebrates 684 million years ago."
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
"Scientists have discovered that tiny ‘microchromosomes’ in birds and reptiles are the same as the tiny chromosomes in a spineless fish-like ancestor that lived 684 million years ago.
https://newsroom.unsw.edu.au/news/science-tech/dust-specks-which-are-actually-building-blocks-our-genome
Um, no, they "suggest" that. Were chromosomes found intact after 684 million years, they wouldn't need to .
On Friday, November 5, 2021 at 4:55:28 PM UTC-7, erik simpson wrote:
On Friday, November 5, 2021 at 1:25:16 PM UTC-7, Glenn wrote:
On Wednesday, November 3, 2021 at 10:10:51 PM UTC-7, erik simpson wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes """Even more astonishingly, they were the same as the tiny chromosomes of Amphioxus – a little fish-like animal with no backbone that last shared a common ancestor with vertebrates 684 million years ago."
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
"Scientists have discovered that tiny ‘microchromosomes’ in birds and reptiles are the same as the tiny chromosomes in a spineless fish-like ancestor that lived 684 million years ago.
https://newsroom.unsw.edu.au/news/science-tech/dust-specks-which-are-actually-building-blocks-our-genome
Um, no, they "suggest" that. Were chromosomes found intact after 684 million years, they wouldn't need to .
Um, no, the scientists didn't say that. You should read the primary sources instead of news releases.So the scientists didn't 'suggest'. Got it. Maybe you should read...oh, never mind.
On Friday, November 5, 2021 at 1:25:16 PM UTC-7, Glenn wrote:
On Wednesday, November 3, 2021 at 10:10:51 PM UTC-7, erik simpson wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes """Even more astonishingly, they were the same as the tiny chromosomes of Amphioxus – a little fish-like animal with no backbone that last shared a common ancestor with vertebrates 684 million years ago."
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
"Scientists have discovered that tiny ‘microchromosomes’ in birds and reptiles are the same as the tiny chromosomes in a spineless fish-like ancestor that lived 684 million years ago.
https://newsroom.unsw.edu.au/news/science-tech/dust-specks-which-are-actually-building-blocks-our-genome
Um, no, they "suggest" that. Were chromosomes found intact after 684 million years, they wouldn't need to .
Um, no, the scientists didn't say that. You should read the primary sources instead of news releases.
On Friday, November 5, 2021 at 6:19:14 PM UTC-7, Glenn wrote:
On Friday, November 5, 2021 at 4:55:28 PM UTC-7, erik simpson wrote:
On Friday, November 5, 2021 at 1:25:16 PM UTC-7, Glenn wrote:So the scientists didn't 'suggest'. Got it. Maybe you should read...oh, never mind.
On Wednesday, November 3, 2021 at 10:10:51 PM UTC-7, erik simpson wrote: >>>>> The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.""Even more astonishingly, they were the same as the tiny chromosomes of Amphioxus – a little fish-like animal with no backbone that last shared a common ancestor with vertebrates 684 million years ago."
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
"Scientists have discovered that tiny ‘microchromosomes’ in birds and reptiles are the same as the tiny chromosomes in a spineless fish-like ancestor that lived 684 million years ago.
https://newsroom.unsw.edu.au/news/science-tech/dust-specks-which-are-actually-building-blocks-our-genome
Um, no, they "suggest" that. Were chromosomes found intact after 684 million years, they wouldn't need to .
Um, no, the scientists didn't say that. You should read the primary sources instead of news releases.
Exactly. Never mind.
On 11/5/21 6:26 PM, erik simpson wrote:
On Friday, November 5, 2021 at 6:19:14 PM UTC-7, Glenn wrote:
On Friday, November 5, 2021 at 4:55:28 PM UTC-7, erik simpson wrote:
On Friday, November 5, 2021 at 1:25:16 PM UTC-7, Glenn wrote:So the scientists didn't 'suggest'. Got it. Maybe you should read...oh, never mind.
On Wednesday, November 3, 2021 at 10:10:51 PM UTC-7, erik simpson wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because""Even more astonishingly, they were the same as the tiny chromosomes of Amphioxus – a little fish-like animal with no backbone that last shared a common ancestor with vertebrates 684 million years ago."
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
"Scientists have discovered that tiny ‘microchromosomes’ in birds and reptiles are the same as the tiny chromosomes in a spineless fish-like ancestor that lived 684 million years ago.
https://newsroom.unsw.edu.au/news/science-tech/dust-specks-which-are-actually-building-blocks-our-genome
Um, no, they "suggest" that. Were chromosomes found intact after 684 million years, they wouldn't need to .
Um, no, the scientists didn't say that. You should read the primary sources instead of news releases.
Exactly. Never mind.
There's really no point in trying to talk to Glenn.
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this >remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I >can't easily digest with my primitive understanding of genetics.
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes"
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I can't easily digest with my primitive understanding of genetics.
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpson <eastside.erik@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
You sound jealous. Just wait for Glenn and the peter to redirect
their attentions back here. I promise I have no problem sharing them
with you.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes"
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
from the "significance" section:
*********************************
Many microchromosomes have been lost independently in turtles, snakes,
and lizards as they have fused with each other or with larger
chromosomes. In mammals they have completely disappeared *********************************
I don't understand what the article means by "lost", "fused", and "disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become
distributed throughout a chromosome and are no longer organized
together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this >> remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I
can't easily digest with my primitive understanding of genetics.
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect
talk.origins is pretty thoroughly corrupted these days.
their attentions back here. I promise I have no problem sharing them
with you.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118from the "significance" section:
*********************************
Many microchromosomes have been lost independently in turtles, snakes,
and lizards as they have fused with each other or with larger
chromosomes. In mammals they have completely disappeared *********************************
I don't understand what the article means by "lost", "fused", and "disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become
distributed throughout a chromosome and are no longer organized
together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this >remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I >can't easily digest with my primitive understanding of genetics.
On 11/4/2021 1:10 AM, erik simpson wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes"
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I can't easily digest with my primitive understanding of genetics.
Molecular clock dates, especially of such a distant time period, must be taken with a hefty grain of salt. The molecular clock works best when calibrated with fossil evidence, but we don't have fossils of chordates
that far back. Admittedly, fossilization is a rare process, and the
further back in time we go the luckier we are to have *any* fossils at
all, so this may just be an error of taphonomy.
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect
talk.origins is pretty thoroughly corrupted these days.
their attentions back here. I promise I have no problem sharing them
with you.
On Saturday, November 6, 2021 at 8:02:01 PM UTC-7, Oxyaena wrote:
On 11/4/2021 1:10 AM, erik simpson wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here because
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes"
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this remarkably precise number comes from as the closest reference to the early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I can't easily digest with my primitive understanding of genetics.
Molecular clock dates, especially of such a distant time period, must be taken with a hefty grain of salt. The molecular clock works best when calibrated with fossil evidence, but we don't have fossils of chordates that far back. Admittedly, fossilization is a rare process, and theAmen! said the congregation. There are no bilaterian fossils known earlier than ~560 Mya,
further back in time we go the luckier we are to have *any* fossils at
all, so this may just be an error of taphonomy.
and they are too small to say much about. The LCA of lancelets (pikaia?, middle cambrian)
and crainiates was obviously much earlier, but molecular clocks work best when calibrated
by fossils bracketing the thing being dated, rather than extrpolating. 684 is over-precise.
maybe "Ediacaran or even earlier" would be better. Even pre-Ediacaran metazoan fossils are
rare and controversial.
On Saturday, November 6, 2021 at 6:42:04 PM UTC-7, 69jp...@gmail.com wrote:
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect
talk.origins is pretty thoroughly corrupted these days.
their attentions back here. I promise I have no problem sharing them
with you.
The article that caught my eye in the "semi-popular" press isfrom the "significance" section:
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
*********************************
Many microchromosomes have been lost independently in turtles, snakes,
and lizards as they have fused with each other or with larger
chromosomes. In mammals they have completely disappeared
*********************************
I don't understand what the article means by "lost", "fused", and
"disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become
distributed throughout a chromosome and are no longer organized
together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this >> >remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution" >> >
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I
can't easily digest with my primitive understanding of genetics.
It's different in Synapsids and Sauropsids. The latter retained the micros as separate specks, but
somewhere along the line of Synapsids (some of) the micro stuff got incorporated into longer chromosomes.
There are lots more crown taxa representing ancient lineages among sauropsids than there sre of
synapsids in the critical early divergence. The oldest monotreme fossil ( a playpoid) is from the
Cretaceous, while Rhynchocephalians date back to the early Triassic. Why the differences between
the genetic histories are so different is a good question that's going to be hard to answer.
On Sat, 6 Nov 2021 20:39:10 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
On Saturday, November 6, 2021 at 6:42:04 PM UTC-7, 69jp...@gmail.com wrote: >> On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect
talk.origins is pretty thoroughly corrupted these days.
their attentions back here. I promise I have no problem sharing them
with you.
The article that caught my eye in the "semi-popular" press isfrom the "significance" section:
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication >> > is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
*********************************
Many microchromosomes have been lost independently in turtles, snakes,
and lizards as they have fused with each other or with larger
chromosomes. In mammals they have completely disappeared
*********************************
I don't understand what the article means by "lost", "fused", and
"disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become
distributed throughout a chromosome and are no longer organized
together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this
remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution" >> >
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I >> >can't easily digest with my primitive understanding of genetics.
It's different in Synapsids and Sauropsids. The latter retained the micros as separate specks, butThanks for your reply, but could you be more precise? You say
somewhere along the line of Synapsids (some of) the micro stuff got incorporated into longer chromosomes.
There are lots more crown taxa representing ancient lineages among sauropsids than there sre of
synapsids in the critical early divergence. The oldest monotreme fossil ( a playpoid) is from the
Cretaceous, while Rhynchocephalians date back to the early Triassic. Why the differences between
the genetic histories are so different is a good question that's going to be hard to answer.
Sauropsids retained the micros as separate specks? Do you mean
physically floating separately and duplicating separately within their nuclei? Or do you mean they retained their composition within a
larger chromosome? If the former, how do microsomes sort evenly
during meiosis? Given how small they are, I would be surprised if
they have their own centromeres.
When you say Synapsids incorporated them into longer chromosomes, do
you mean the microsomes retained their composition within larger chromosomes? If so, what does the article mean when it says
microsomes "completely disappeared" in mammals? What evidence is
there microsomes ever existed in mammals?
On Sunday, November 7, 2021 at 9:22:27 AM UTC-8, 69jp...@gmail.com wrote:comparisons, and chromosome conformation capture, to trace their origin and fate in genomes of reptiles, birds, and mammals. We find that microchromosomes as well as macrochromosomes are highly conserved across birds and share synteny with single small
On Sat, 6 Nov 2021 20:39:10 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
On Saturday, November 6, 2021 at 6:42:04 PM UTC-7, 69jp...@gmail.com wrote:Thanks for your reply, but could you be more precise? You say
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect
talk.origins is pretty thoroughly corrupted these days.
their attentions back here. I promise I have no problem sharing them
with you.
The article that caught my eye in the "semi-popular" press isfrom the "significance" section:
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication >> >> > is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
*********************************
Many microchromosomes have been lost independently in turtles, snakes, >> >> and lizards as they have fused with each other or with larger
chromosomes. In mammals they have completely disappeared
*********************************
I don't understand what the article means by "lost", "fused", and
"disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become
distributed throughout a chromosome and are no longer organized
together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this
remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I >> >> >can't easily digest with my primitive understanding of genetics.
It's different in Synapsids and Sauropsids. The latter retained the micros as separate specks, but
somewhere along the line of Synapsids (some of) the micro stuff got incorporated into longer chromosomes.
There are lots more crown taxa representing ancient lineages among sauropsids than there sre of
synapsids in the critical early divergence. The oldest monotreme fossil ( a playpoid) is from the
Cretaceous, while Rhynchocephalians date back to the early Triassic. Why the differences between
the genetic histories are so different is a good question that's going to be hard to answer.
Sauropsids retained the micros as separate specks? Do you mean
physically floating separately and duplicating separately within their
nuclei? Or do you mean they retained their composition within a
larger chromosome? If the former, how do microsomes sort evenly
during meiosis? Given how small they are, I would be surprised if
they have their own centromeres.
When you say Synapsids incorporated them into longer chromosomes, do
you mean the microsomes retained their composition within larger
chromosomes? If so, what does the article mean when it says
microsomes "completely disappeared" in mammals? What evidence is
there microsomes ever existed in mammals?
I'm apprehensive about answering definitively, but I'd reply "yes" to both your questions.
The abstract from the PNAS citation:
"Microchromosomes, once considered unimportant shreds of the chicken genome, are gene-rich elements with a high GC content and few transposable elements. Their origin has been debated for decades. We used cytological and whole-genome sequence
interphase and during mitosis and meiosis. This reflects higher interaction between microchromosomes than with macrochromosomes, as observed by chromosome conformation capture, and suggests some functional coherence. In highly rearranged genomes fusedmicrochromo- somes retain most ancestral characteristics, but these may erode over evolutionary time; surprisingly, de novo microchromosomes have rapidly adopted high interaction. Some chromosomes of early-branching monotreme mammals align to several
On Sun, 7 Nov 2021 10:16:28 -0800 (PST), erik simpsoncomparisons, and chromosome conformation capture, to trace their origin and fate in genomes of reptiles, birds, and mammals. We find that microchromosomes as well as macrochromosomes are highly conserved across birds and share synteny with single small
<eastsi...@gmail.com> wrote:
On Sunday, November 7, 2021 at 9:22:27 AM UTC-8, 69jp...@gmail.com wrote: >> On Sat, 6 Nov 2021 20:39:10 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
On Saturday, November 6, 2021 at 6:42:04 PM UTC-7, 69jp...@gmail.com wrote:Thanks for your reply, but could you be more precise? You say
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect
talk.origins is pretty thoroughly corrupted these days.
their attentions back here. I promise I have no problem sharing them >> >> with you.
The article that caught my eye in the "semi-popular" press isfrom the "significance" section:
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
*********************************
Many microchromosomes have been lost independently in turtles, snakes, >> >> and lizards as they have fused with each other or with larger
chromosomes. In mammals they have completely disappeared
*********************************
I don't understand what the article means by "lost", "fused", and
"disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become
distributed throughout a chromosome and are no longer organized
together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this
remarkably precise number comes from as the closest reference to the >> >> >early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I
can't easily digest with my primitive understanding of genetics.
It's different in Synapsids and Sauropsids. The latter retained the micros as separate specks, but
somewhere along the line of Synapsids (some of) the micro stuff got incorporated into longer chromosomes.
There are lots more crown taxa representing ancient lineages among sauropsids than there sre of
synapsids in the critical early divergence. The oldest monotreme fossil ( a playpoid) is from the
Cretaceous, while Rhynchocephalians date back to the early Triassic. Why the differences between
the genetic histories are so different is a good question that's going to be hard to answer.
Sauropsids retained the micros as separate specks? Do you mean
physically floating separately and duplicating separately within their
nuclei? Or do you mean they retained their composition within a
larger chromosome? If the former, how do microsomes sort evenly
during meiosis? Given how small they are, I would be surprised if
they have their own centromeres.
When you say Synapsids incorporated them into longer chromosomes, do
you mean the microsomes retained their composition within larger
chromosomes? If so, what does the article mean when it says
microsomes "completely disappeared" in mammals? What evidence is
there microsomes ever existed in mammals?
I'm apprehensive about answering definitively, but I'd reply "yes" to both your questions.
The abstract from the PNAS citation:
"Microchromosomes, once considered unimportant shreds of the chicken genome, are gene-rich elements with a high GC content and few transposable elements. Their origin has been debated for decades. We used cytological and whole-genome sequence
microchromo- somes retain most ancestral characteristics, but these may erode over evolutionary time; surprisingly, de novo microchromosomes have rapidly adopted high interaction. Some chromosomes of early-branching monotreme mammals align to severalinterphase and during mitosis and meiosis. This reflects higher interaction between microchromosomes than with macrochromosomes, as observed by chromosome conformation capture, and suggests some functional coherence. In highly rearranged genomes fused
I read the abstract from the PNAS citation before I posted my
questions. If simply reading it answered my questions, I would not
have asked them. They are not "yes/no" type questions. I regret if
you think my questions are out of line.
On Saturday, November 6, 2021 at 8:49:06 PM UTC-7, erik simpson wrote:
On Saturday, November 6, 2021 at 8:02:01 PM UTC-7, Oxyaena wrote:
On 11/4/2021 1:10 AM, erik simpson wrote:Amen! said the congregation. There are no bilaterian fossils known earlier than ~560 Mya,
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseMolecular clock dates, especially of such a distant time period, must be >>> taken with a hefty grain of salt. The molecular clock works best when
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes"
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication >>>> is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this >>>> remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution" >>>>
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I >>>> can't easily digest with my primitive understanding of genetics.
calibrated with fossil evidence, but we don't have fossils of chordates
that far back. Admittedly, fossilization is a rare process, and the
further back in time we go the luckier we are to have *any* fossils at
all, so this may just be an error of taphonomy.
and they are too small to say much about. The LCA of lancelets (pikaia?, middle cambrian)
and crainiates was obviously much earlier, but molecular clocks work best when calibrated
by fossils bracketing the thing being dated, rather than extrpolating. 684 is over-precise.
maybe "Ediacaran or even earlier" would be better. Even pre-Ediacaran metazoan fossils are
rare and controversial.
Well, that was confused. My only defense is the approach of the end of DST rattled me. We actually
have lots of crown taxa whose origins antedate the separation of lancelets from vertebrates; protostomes,
cnidarians, placozoans, sponges, ctenophorans. The 684 Mya number seems much too large.
On Sunday, November 7, 2021 at 4:56:02 PM UTC-8, John Harshman wrote:comparisons, and chromosome conformation capture, to trace their origin and fate in genomes of reptiles, birds, and mammals. We find that microchromosomes as well as macrochromosomes are highly conserved across birds and share synteny with single small
On 11/7/21 2:26 PM, erik simpson wrote:
On Sunday, November 7, 2021 at 12:26:45 PM UTC-8, 69jp...@gmail.com wrote:
On Sun, 7 Nov 2021 10:16:28 -0800 (PST), erik simpson
<eastsi...@gmail.com> wrote:
On Sunday, November 7, 2021 at 9:22:27 AM UTC-8, 69jp...@gmail.com wrote:
On Sat, 6 Nov 2021 20:39:10 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
On Saturday, November 6, 2021 at 6:42:04 PM UTC-7, 69jp...@gmail.com wrote:Thanks for your reply, but could you be more precise? You say
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpsonIt's different in Synapsids and Sauropsids. The latter retained the micros as separate specks, but
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect >>>>>> their attentions back here. I promise I have no problem sharing them
talk.origins is pretty thoroughly corrupted these days.
with you.
The article that caught my eye in the "semi-popular" press is >>>>>>>from the "significance" section:
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
*********************************
Many microchromosomes have been lost independently in turtles, snakes,
and lizards as they have fused with each other or with larger >>>>>> chromosomes. In mammals they have completely disappeared
*********************************
I don't understand what the article means by "lost", "fused", and >>>>>> "disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become >>>>>> distributed throughout a chromosome and are no longer organized >>>>>> together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this
remarkably precise number comes from as the closest reference to the
early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I
can't easily digest with my primitive understanding of genetics. >>>>>
somewhere along the line of Synapsids (some of) the micro stuff got incorporated into longer chromosomes.
There are lots more crown taxa representing ancient lineages among sauropsids than there sre of
synapsids in the critical early divergence. The oldest monotreme fossil ( a playpoid) is from the
Cretaceous, while Rhynchocephalians date back to the early Triassic. Why the differences between
the genetic histories are so different is a good question that's going to be hard to answer.
Sauropsids retained the micros as separate specks? Do you mean
physically floating separately and duplicating separately within their
nuclei? Or do you mean they retained their composition within a
larger chromosome? If the former, how do microsomes sort evenly
during meiosis? Given how small they are, I would be surprised if >>>> they have their own centromeres.
When you say Synapsids incorporated them into longer chromosomes, do >>>> you mean the microsomes retained their composition within larger
chromosomes? If so, what does the article mean when it says
microsomes "completely disappeared" in mammals? What evidence is
there microsomes ever existed in mammals?
I'm apprehensive about answering definitively, but I'd reply "yes" to both your questions.
The abstract from the PNAS citation:
"Microchromosomes, once considered unimportant shreds of the chicken genome, are gene-rich elements with a high GC content and few transposable elements. Their origin has been debated for decades. We used cytological and whole-genome sequence
fused microchromo- somes retain most ancestral characteristics, but these may erode over evolutionary time; surprisingly, de novo microchromosomes have rapidly adopted high interaction. Some chromosomes of early-branching monotreme mammals align tointerphase and during mitosis and meiosis. This reflects higher interaction between microchromosomes than with macrochromosomes, as observed by chromosome conformation capture, and suggests some functional coherence. In highly rearranged genomes
I read the abstract from the PNAS citation before I posted my
questions. If simply reading it answered my questions, I would not
have asked them. They are not "yes/no" type questions. I regret if
you think my questions are out of line.
I didn't mean to imply that your questions are out of line. As I pointed out in the original post,
I consider my proficiency with genetic terminology inadequate to give an answer without some
possibility that I read it wrong. Platypoids are mammals, and some of the microchromosomes present in
the earliest synapsids are still to be seen tin their heir genome, but incorporated in longer chromosomes. The fact
that the paper doesn't mention any idntification of microchromasomes in the genome of more derived
mammals would seem to suggest that they've disappeared, or have been modified beyond recognition.
Mammals do not have microchromosomes, but they have regions of their macrochromosomes that are homologous to some of the microchromosomes present in sauropsids.Are the homologous regions been identified in mammals other than monotremes? If so, I
missed that. I'm also curious to know how deep in the tree microchromosomes go. I haven't
found any reference for their presence in Ambulacraria or other more basal deuterostomes.
On 11/7/21 2:26 PM, erik simpson wrote:comparisons, and chromosome conformation capture, to trace their origin and fate in genomes of reptiles, birds, and mammals. We find that microchromosomes as well as macrochromosomes are highly conserved across birds and share synteny with single small
On Sunday, November 7, 2021 at 12:26:45 PM UTC-8, 69jp...@gmail.com wrote:
On Sun, 7 Nov 2021 10:16:28 -0800 (PST), erik simpson
<eastsi...@gmail.com> wrote:
On Sunday, November 7, 2021 at 9:22:27 AM UTC-8, 69jp...@gmail.com wrote:
On Sat, 6 Nov 2021 20:39:10 -0700 (PDT), erik simpson
<eastsi...@gmail.com> wrote:
On Saturday, November 6, 2021 at 6:42:04 PM UTC-7, 69jp...@gmail.com wrote:Thanks for your reply, but could you be more precise? You say
On Wed, 3 Nov 2021 22:10:50 -0700 (PDT), erik simpsonIt's different in Synapsids and Sauropsids. The latter retained the micros as separate specks, but
<eastsi...@gmail.com> wrote:
The articles I reference here aren't really paleontology, and this post might actually be more appropriate for talk.origins, but i'm putting it here becauseYou sound jealous. Just wait for Glenn and the peter to redirect >>>>>> their attentions back here. I promise I have no problem sharing them >>>>>> with you.
talk.origins is pretty thoroughly corrupted these days.
The article that caught my eye in the "semi-popular" press is >>>>>>>from the "significance" section:
"'Useless Specks of Dust' Turn Out to Be Building Blocks of All Vertebrate Genomes "
https://www.sciencealert.com/useless-specks-of-dust-turn-out-to-be-ancient-building-blocks-of-all-vertebrate-genomes
The useless specks are microchromosomes, and the scientific publication
is
"Microchromosomes are building blocks of bird, reptile, and mammal chromosomes"
https://www.pnas.org/content/118/45/e2112494118
*********************************
Many microchromosomes have been lost independently in turtles, snakes,
and lizards as they have fused with each other or with larger
chromosomes. In mammals they have completely disappeared
*********************************
I don't understand what the article means by "lost", "fused", and >>>>>> "disappeared". Does the article mean the genes within the
microchromosomes are lost, or does it mean the genes have become >>>>>> distributed throughout a chromosome and are no longer organized >>>>>> together?
One of the things that really caught my attention was the result that amphioxus (the lancelet) turns out to be less closely related to vertebrates
than tunicates, with a branching date of 684 Mya. I can't find where this
remarkably precise number comes from as the closest reference to the >>>>>>> early divergence seems to be
"Deeply conserved synteny resolves early events in vertebrate evolution"
https://www.nature.com/articles/s41559-020-1156-z
which doesn't provide the number. Anyway, a fascinating subject which I
can't easily digest with my primitive understanding of genetics. >>>>>
somewhere along the line of Synapsids (some of) the micro stuff got incorporated into longer chromosomes.
There are lots more crown taxa representing ancient lineages among sauropsids than there sre of
synapsids in the critical early divergence. The oldest monotreme fossil ( a playpoid) is from the
Cretaceous, while Rhynchocephalians date back to the early Triassic. Why the differences between
the genetic histories are so different is a good question that's going to be hard to answer.
Sauropsids retained the micros as separate specks? Do you mean
physically floating separately and duplicating separately within their >>>> nuclei? Or do you mean they retained their composition within a
larger chromosome? If the former, how do microsomes sort evenly
during meiosis? Given how small they are, I would be surprised if
they have their own centromeres.
When you say Synapsids incorporated them into longer chromosomes, do >>>> you mean the microsomes retained their composition within larger
chromosomes? If so, what does the article mean when it says
microsomes "completely disappeared" in mammals? What evidence is
there microsomes ever existed in mammals?
I'm apprehensive about answering definitively, but I'd reply "yes" to both your questions.
The abstract from the PNAS citation:
"Microchromosomes, once considered unimportant shreds of the chicken genome, are gene-rich elements with a high GC content and few transposable elements. Their origin has been debated for decades. We used cytological and whole-genome sequence
fused microchromo- somes retain most ancestral characteristics, but these may erode over evolutionary time; surprisingly, de novo microchromosomes have rapidly adopted high interaction. Some chromosomes of early-branching monotreme mammals align tointerphase and during mitosis and meiosis. This reflects higher interaction between microchromosomes than with macrochromosomes, as observed by chromosome conformation capture, and suggests some functional coherence. In highly rearranged genomes
I read the abstract from the PNAS citation before I posted my
questions. If simply reading it answered my questions, I would not
have asked them. They are not "yes/no" type questions. I regret if
you think my questions are out of line.
I didn't mean to imply that your questions are out of line. As I pointed out in the original post,
I consider my proficiency with genetic terminology inadequate to give an answer without some
possibility that I read it wrong. Platypoids are mammals, and some of the microchromosomes present in
the earliest synapsids are still to be seen tin their heir genome, but incorporated in longer chromosomes. The fact
that the paper doesn't mention any idntification of microchromasomes in the genome of more derived
mammals would seem to suggest that they've disappeared, or have been modified beyond recognition.
Mammals do not have microchromosomes, but they have regions of their macrochromosomes that are homologous to some of the microchromosomes
present in sauropsids.
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