Freethought & Rationalism Archive

Kevin Dorner · 01-31-2002, 05:16 AM

While poking around for news stories, I found <a href="http://bio.com/newsfeatures/newsfeatures_research.jhtml;jsessionid=LYVCFH3UUAC CLR3FQLMCFEWHUWBNSIV0?action=view&contentItem=1781 6666&Page=1" target="_blank">this Bio.com article</a> which might be interesting material for the debaters here.

I say this as creationists/ID advocates (most notably Michael Behe) still fall back on the blood clotting process as being an example of "irreducible complexity." Enjoy...

Automaton · 01-31-2002, 05:32 AM

Yeah Dr. Behe, there is no known way that the blood clotting cascade could have evolved, step-by-step, from unrelated enzymes.

So who's being "dogmatic"?

Oolon Colluphid · 01-31-2002, 05:38 AM

Excellent stuff Kevin! Thanks for that!

Quote:

A gene that makes human blood clot also is found in bloodless fruit flies and helps venomous cone snails produce an experimental drug against epilepsy.

Another one for my list of pointless features then! Fruitflies and cone snails don't have blood, and humans and fruitflies don't make poisons! "Oi! Creationists! GOTCHA!"

Quote:

The finding also supports the notion that "junk DNA"—portions of the genetic code that are within genes but have no apparent function—arose early in evolution, namely more than 500 million years ago, rather than later, as some have argued.

One for you then, theyeti.

Thanks again Kevin!

Oolon

theyeti · 01-31-2002, 06:07 AM

The notion that the introns existed 540 million years ago is entirely consistent with the introns late theory. For introns early to be correct, they would have had to exist circa 3.5 billion years ago, which is a bit of a stretch if you ask me. The only introns that qualify as being "ancient" are those that can be infered to have existed in both eukaryotes and prokaryotes, thus predating the split of these two lineages. The current consensus is that some introns are ancient, but most have been added throughout evolution. The one's referred to here would be in the latter category, unless the intron/exon arrangement can be inferred in all organisms, not just in metazoa.

Quote:

Finding great similarities in the junk DNA of three kinds of animals that evolved along different paths starting 540 million years ago indicates the junk DNA in the human GGC gene is ancient, and implies "almost all human junk [DNA] might be old junk," Olivera said.

Putting the "ancient" part aside, this is clearly an unwarranted extrapolation. There are introns that are known to be recent, so finding some that are old just adds to the current consensus that they are of varying age.

Anyway, I don't agree with their conclusions about the IE/IL debate, but it's still a cool article (full text <a href="http://www.pnas.org/cgi/content/full/022637099v1" target="_blank">here</a>. Thanks for posting it, Kevin!

theyeti

P.S. I found this statement interesting:

Quote:

This finding raises the intriguing question of whether most introns in other human genes have a similarly ancient lineage. Our results suggest that Drosophila (and perhaps, other insects) may not be the appropriate invertebrate standard for evaluating whether vertebrate introns are likely to be relatively recent or more ancient than the Cambrian explosion.

There are a lot of researchers who study the intron thing in more detail that think that the emergence of spliceosomal introns is responsible for the Cambrian explosion, because they help facilitate exon shuffling. I'll post some info on that later.

bluefugue · 01-31-2002, 06:27 AM

Fruit flies don't have blood? Does that go for all insects? Does that mean they don't have circulatory systems? I know insect respiration is completely different from vertebrate respiration, but I didn't know they had no blood at all... what about earthworms? They have about 10 hearts... what do the hearts pump? Are they similar in function and origin to vertebrate hearts, or similar only in name?... Are earthworms more closely related to us than arthropods?

Kevin Dorner · 01-31-2002, 06:47 AM

Fruit flies and other insects have a (usually) straw-coloured fluid called hemolymph that transports nutrients. Their "circulatory" systems don't have arteries or veins. As they breathe through spiracles (pores) and insects are small enough that they don't have much a deep interior, their circulatory system can be as basic as this and still suffice and their "blood" doesn't transport oxygen so doesn't have oxygen-transporting cells.

Although you might see red goo when you swat a fly, that's from their eyes. Ick!

Edit: Oh, and Oolon and theyeti, glad you liked the article.

[ January 31, 2002: Message edited by: Kevin Dorner ]

Peez · 01-31-2002, 08:44 AM

Quote:

IesusDomini
Fruit flies don't have blood?

This is something of a semantic question. Insects do have a circulating fluid that is sometimes called blood. Insect "blood" is very different from vertebrate "blood," however, and is sometimes called hemolymph to distinguish it.

Quote:

Does that go for all insects?

Yes, though there are variants.

Quote:

Does that mean they don't have circulatory systems?

No. They have open circulatory systems in which blood/hemolymph is pumped by the heart through vessels which then release it into the tissues, it then filters through the tissues until picked up by the heart again.

Quote:

I know insect respiration is completely different from vertebrate respiration, but I didn't know they had no blood at all...

Insects have a system of tubes called tracheae which permeate their body and open to the outside. These allow the exchange of oxygen and carbon dioxide with the environment.

Quote:

what about earthworms? They have about 10 hearts... what do the hearts pump? Are they similar in function and origin to vertebrate hearts, or similar only in name?...

Earthworms do have ten hearts, each much simpler in structure to ours. They have closed circulatory systems, like us, and blood plays an important roll in moving oxygen about the body.

Quote:

Are earthworms more closely related to us than arthropods?

No, they are more closely related to each other than they are to us.

Peez

[ January 31, 2002: Message edited by: Peez ]

rafe gutman · 01-31-2002, 12:36 PM

cool article, i forwarded it to someone in the doolittle lab. we'll see what he thinks of this.

quick question: if worms have a closed circulatory system, did they evolve it independently of us?

theyeti · 01-31-2002, 12:41 PM

Okay, introns and the Cambrian explosion. This is basically cut and paste from a project that I'm working on:

In his review of exon-shuffling, Patthy (1999) notes that the likely appearance of spliceosomal introns correlates nicely to the explosive radiation of metazoa during the Cambrian. Self-splicing introns that predate the evolution of the spliceosome are not likely to be amenable to exon-shuffling; thus the great amount of time between the appearance of life and the explosive radiation of metazoa may be due in part to the necessity of the spliceosome. Patthy remarks:

Quote:

In summary, the results suggest that exon-shuffling acquired major significance at the time of metazoan radiation. It is interesting to note that the rise of exon-shuffling coincides with a spectacular burst of evolutionary creativity: the Big Bang of metazoan radiation. It seems probable that modular protein evolution by exon-shuffling has contributed significantly to this accelerated evolution of metazoa, since it facilitated the rapid construction of multidomain extracellular and cell surface proteins that are indispensable for multicellularity.

Similar sentiments abound. This idea relates in particular to the introns-early vs. introns-late debate, as the current consensus (as much as there can be one) seems to be an intermediate view that holds that while some introns probably are ancient, the vast majority have been acquired since the divergence of prokaryotes and eukaryotes and continue to do so today. Gilbert et al. (1997) explain...

Quote:

There are three possible scenarios for the evolutionary history of introns. One is that there were introns at the very beginning of evolution and that during evolution they were lost or, possibly, mostly lost and some added. This complex of ideas is "The Exon Theory of Genes" (2). The extreme alternative view is that introns were added very late in evolution, even in the last few million years, and thus have nothing to do with the rearrangement of pieces of genes. There is no exon shuffling on this picture. A third, intermediate view, popular in its own right, is that the introns arose at the initiation of multicellularity. In this picture, the Cambrian explosion used introns to create exon shuffling and a profusion of new genes.

...which all in all shows that the ability of introns to promote exon-shuffling is not only likely responsible for that rather unique event (frequently referred to by ID/creationism as evidence of the �sudden appearance� of animal �designs�, as if nothing has changed since then), but is also likely responsible, or at least indispensable, for the great deal of evolutionary change among multicellular eukaryotes since.

Patthy, La�szlo �, Genome evolution and the evolution of exon-shuffling �a review. <a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=105709 89&dopt=Abstract" target="_blank">Gene 238 (1999) 103�114.</a>

Gilbert W, de Souza SJ, Long M., Origin of genes. Proc Natl Acad Sci U S A 1997 Jul 22;94(15):7698-703. <a href="http://www.pnas.org/cgi/content/full/94/15/7698" target="_blank">Full Text</a>

theyeti

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[ January 31, 2002: Message edited by: theyeti ]

lpetrich · 01-31-2002, 05:02 PM

The next question is what these genes do. Since fruit flies and snails have some circulatory fluid, could this mean that they also have a blood-clotting system?

One interesting conundrum in this regard is that yeast, IIRC, have a very insulin-like gene. However, yeast are single-celled organisms which do not need to signal each other about their sugar consumption.

[ January 31, 2002: Message edited by: lpetrich ]

01-31-2002, 05:16 AM	#1
Kevin Dorner Senior Member Join Date: Dec 2001 Location: Toronto, Ontario, Canada Posts: 762	Article: Human Blood-Clotting Gene Found In Bloodless Species While poking around for news stories, I found <a href="http://bio.com/newsfeatures/newsfeatures_research.jhtml;jsessionid=LYVCFH3UUAC CLR3FQLMCFEWHUWBNSIV0?action=view&contentItem=1781 6666&Page=1" target="_blank">this Bio.com article</a> which might be interesting material for the debaters here. I say this as creationists/ID advocates (most notably Michael Behe) still fall back on the blood clotting process as being an example of "irreducible complexity." Enjoy...

01-31-2002, 06:47 AM	#6
Kevin Dorner Senior Member Join Date: Dec 2001 Location: Toronto, Ontario, Canada Posts: 762	Fruit flies and other insects have a (usually) straw-coloured fluid called hemolymph that transports nutrients. Their "circulatory" systems don't have arteries or veins. As they breathe through spiracles (pores) and insects are small enough that they don't have much a deep interior, their circulatory system can be as basic as this and still suffice and their "blood" doesn't transport oxygen so doesn't have oxygen-transporting cells. Although you might see red goo when you swat a fly, that's from their eyes. Ick! Edit: Oh, and Oolon and theyeti, glad you liked the article. [ January 31, 2002: Message edited by: Kevin Dorner ]</p>

01-31-2002, 05:02 PM	#10
lpetrich Contributor Join Date: Jul 2000 Location: Lebanon, OR, USA Posts: 16,829	The next question is what these genes do. Since fruit flies and snails have some circulatory fluid, could this mean that they also have a blood-clotting system? One interesting conundrum in this regard is that yeast, IIRC, have a very insulin-like gene. However, yeast are single-celled organisms which do not need to signal each other about their sugar consumption. [ January 31, 2002: Message edited by: lpetrich ]</p>

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01-31-2002, 05:32 AM	#2
Automaton Senior Member Join Date: Jan 2002 Posts: 717	Yeah Dr. Behe, there is no known way that the blood clotting cascade could have evolved, step-by-step, from unrelated enzymes. So who's being "dogmatic"?

01-31-2002, 06:27 AM	#5
bluefugue Veteran Member Join Date: Aug 2001 Location: Los Angeles Posts: 1,427	Fruit flies don't have blood? Does that go for all insects? Does that mean they don't have circulatory systems? I know insect respiration is completely different from vertebrate respiration, but I didn't know they had no blood at all... what about earthworms? They have about 10 hearts... what do the hearts pump? Are they similar in function and origin to vertebrate hearts, or similar only in name?... Are earthworms more closely related to us than arthropods?

01-31-2002, 12:36 PM	#8
rafe gutman Junior Member Join Date: May 2001 Location: La Jolla, CA Posts: 72	cool article, i forwarded it to someone in the doolittle lab. we'll see what he thinks of this. quick question: if worms have a closed circulatory system, did they evolve it independently of us?

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