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<a href="http://creationtalk.com/ubb/Forum2/HTML/000001-2.html" target="_blank">http://creationtalk.com/ubb/Forum2/HTML/000001-2.html</a>

In response, another poster stated:

Is Brush right here? Or is he being quoted out of context?

Oolon Colluphid

Of course they're different. One's scales, the other's feathers. Sounds out of context. I've not had time to absorb it, but this may be useful:

<a href="http://www.eurekah.com/chapter.php?chapid=594&bookid=53&catid=20" target="_blank">www.eurekah.com/chapter.php?chapid=594&bookid=53&catid=20</a>

Cheers, Oolon

KC

What Brush is saying is that feathers seem more closely related to scutes (the scales one sees on bird feet, which are not the same as reptilian scales). Reptiles do possess scutes, however, (crocodiles, for example), as did dinosaurs.

<a href="http://www.dinosauria.com/jdp/archie/scutes.htm" target="_blank">Feathers and Scutes</a>

Cheers,

KC

Randy

Now keratins are something I know a little bit about and I have the Brush paper. This is rather classic out of context quoting and it is found in Sarfati’s book Refuting Evolution.

Brush is trying to argue that feathers may have evolved from directly from skin, the way hair apparently did, rather than from scale. While phi-keratins are very different from alpha keratins, they are very closely related to the beta keratins that are found in the skin of all reptiles and the scale of birds. They are shorted because of the deletion of an approximately 4,000 molecular weight repeating tripeptide(Gly-Gly-X) that followed a duplication of the original beta keratin gene.

Here are a few more quotes from the Brush paper.

Further, the proteins and genes of feather and scale ….are close enough to imply a common ancestor…….

All proteins in the family share a great deal of sequence similarity…

Subsequent to its appearance the gene was duplicated. One or more of the duplicates then incurred a deletion of the tripeptide portion. This provides a basis for two distinct size categories associated with the different tissues.

The quotes above are the parts of the paper that creatonists always leave out. I wonder why?

Randy
Here are some further references added in edit
Chen, C.W., Jung, H.S., Jiang, T.X. and Chuong, C.M. (1997) Asymmetric expression of Notch/Delta/Serrate is associated with the anterior-posterior axis of feather buds. Dev Biol 188, 181.

Chuong, C.M., Chodankar, R., Widelitz, R.B. and Jiang, T.X. (2000) Evo-Devo of feathers and scales: building complex epithelial appendages. Current Opinions in Genetics and Development 10, 449.

Chuong, C.M. and Noveen, A. (1999) Phenotypic determination of epithelial appendages: genes, developmental pathways, and evolution. J Investig Dermatol Symp Proc 4, 307.

Jones, T.D., Ruben, J.A., Martin, L.D., Kurochkin, E.N., Feduccia, A., Maderson, P.F., Hillenius, W.J., Geist, N.R. and Alifanov, V. (2000) Nonavian feathers in a late Triassic archosaur. Science 288, 2202.

Prum, R.O. (1999) Development and evolutionary origin of feathers. J Exp Zool 285, 291.

Widelitz, R.B., Jiang, T.X., Lu, J. and Chuong, C.M. (2000) beta-catenin in epithelial morphogenesis: Conversion of part of avian foot scales into feather buds with a mutated beta-catenin. Dev Biol 219, 98.

[ August 19, 2002: Message edited by: Randy ]</p>

Dr.GH

Thanks to all for some very useful references.


Gary

Randy

As a PS to my post, the reason I suspected the Brush quote was seriously out of context and ordered the paper is that I knew that feather and scuttate scale keratins cross react in Western Blots. This has been known since at least the mid 1980's and is not surprising since they are so closely related. (See Biology of the Integument 2 Vertebrates, Bereiter-Hahn, Matoltsy and Richards eds. Springer Verlag 1986 p 217.)

I really know more about mammalian hair and skin keratins, which are purely alpha, than I do about beta keratins. Alpha keratins are part of the intermediate filament protein family and first appear in primative chordates such as amphioxus. Beta keratins only appear in birds and reptiles.

Hair keratin undergoes a transition from alpha helix to beta sheet when extended and set in steam. This is how Astbury discovered the alpha helix and beta sheet X-ray patterns.

One of the few genes known to be active in chimps and a pseudogene in humans is a gene for one of the type I hair keratins (Winter et al(2001) Human Genetics 108:37-42). I suppose that's more aobut keratins than anyone really wanted to know but I find them a very interesting subject.
Randy

Nic Tamzek

Whoa. A hair protein expert.

Obscure Question of the Month for Randy:

OK. My old The World of the Cell cell bio. textbook has a diagram of the Structure of Hair on p. 53.

Alpha-keratin forms an alpha helix.
3 of these form a protofibril

and then, the protofibrils form a microfibril, but by forming in a 9+2 pattern. A bunch of microfibrils form a macrofibril and a bunch of those form a hair.

I am interested in this because 9+2 is the same arrangement as microtubules in a (standard) cilium. The scale of microtubules and protofibrils might be about the same (correct me if I'm wrong, I may well be). So I see two potential explanations:

1) Common patterning mechanism for the 9+2 structure of keratin microfibrils and MT cilia (although this would be wild if it were true IMO)

...or...

2) There is something fundamental about macromolecular fibers such that 9+2 is a common pattern that emerges. Cilia expert Azfelius pointed out long ago that if you put quarters on a table, the minimum number of quarters required to put a circle of touching quarters around two touching quarters is 9.

Any thoughts? Or have any keratin authorities that you know of had any thoughts?

nic

Valentine Pontifex

Sarfati is starting to make <a href="http://www.talkorigins.org/origins/faqs-index.html#gish" target="_blank">Duane Gish</a> look like a boy scout.

In any event, I seached AiG and found that Sarfati uses the quote in question at:

<a href="http://answersingenesis.org/docs/491.asp" target="_blank">http://answersingenesis.org/docs/491.asp</a>

[ August 19, 2002: Message edited by: LordValentine ]</p>

Randy

Unfortunately, your information is a bit outdated. Text books from way back in the early 90’s will have the three chain protofibril picture, which changed in the literature way back in the mid to late 80’s or so. Does that make you feel old? It does me. Like hearing oldies from the 80's on the radio.

The keratin alpha helices form a coiled coil in both skin and hair. This two chain structure is virtually identical to that formed by other intermediate filament proteins and was indentified in other intermediate filaments by Francis Crick in the late 60's IIRC. The coiled coils are parallel and in register. This structure persists until the final keratization process occurs. During keratinization the coiled coils form a tetramer and then the tetramers interact to form octamers, four octomers form the 32 chain structure of the microfibril. In the stratum granulosum of the skin this occurs by interaction with a protein called filaggrin, an acronym for filament aggregating protein. The picture is not so clear in hair but the 32 chain structure forms somehow in the cortical cells perhaps under the influence of tricohyalin. I recently wrote a book chapter on the chemistry and physics of hair so I can give you a lot of references later if you want them.
Randy

Nic Tamzek

It is indeed a textbook from the early 1990's.

To cut to the chase, are you telling me that the 9+2 structure of a microfibril in hair (clearly labled as such in the textbook) in fact doesn't exist and thus there is no coincidence to puzzle over?

(I kind of figured that they wouldn't stick a 9+2 structure in the graphic unless they had electron microscopy or something documenting it...)

Thanks for your rather specialized help, BTW
nic