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Author Topic:   Hox genes and different taxa
Biofreak Japan
Inactive Member


Message 16 of 17 (188491)
02-25-2005 11:43 AM
Reply to: Message 4 by Andya Primanda
11-18-2004 10:52 AM


Untuk Pak Andya
Terribly sorry for using this message board to send a personal message - I have been trying to reach Mr. Andya Primanda through the email address provided in this site, but the messages bounced back. Hence below, I am writing a message in Indonesian to Mr. Andra. To the Administrators, please don't erase this message - I really want to get in touch with Mr. Andya.
Pak, Salam Kenal, saya mahasiswa S3 di Universitas Tokyo, mempelajari Developmental Genetics dan Molecular Embryology. Saya tertarik dengan pesan2 Bapak yang ditulis di homepage ini, dan kalau tidak keberatan ingin berkenalan dan berhubungan dengan Bapak? Saya ingin sekali minta diajari bermacam2 dan berdiskusi soal evolusi. Apakah Bapak sekarang masih berada di Indonesia / Jakarta?
Terima kasih.
regards,
Dave

This message is a reply to:
 Message 4 by Andya Primanda, posted 11-18-2004 10:52 AM Andya Primanda has not replied

  
Loudmouth
Inactive Member


Message 17 of 17 (188533)
02-25-2005 3:53 PM
Reply to: Message 1 by SAGREB
11-17-2004 4:31 PM


quote:
I wonder if anyone is familiar with what kind of changes of the hox genes that are responsible for a new family, order or class to evolve? Ive heard that changes in the downstream region of hox genes is caracteristic for species within a family. For different families in the same order, for example dogs, cats or bears, Ive heard that it is mutations within the hox genes themselves. What about bigger morphological differences, such as whales and artiodactyles? What differs there?
There is a great section in the 22 Oct 2004 issue of Science. The section is called "Genes in Action". It outlines the effect of transcription factors (ie enhancers) of hox genes, and also outlines early embryonic development with respect to gene cascades. One section I found interesting is found on pg's 634-635 discussing the different morphology between starfish and urchins:
Yet subtle variations have had a big impact. For example, there's a five-gene circuit both species share. A key gene in this pathway is otx, and it sets off the circuit in the sea urchin and the starfish. Hinman has found a tiny change in this enhancer. Between the two species, this enhancer varies by just one binding site, for a transcription factor called t-brain. The starfish has this binding site; the sea urchin does not. In the sea urchin, t-brain works in concert with other regulatory genes and sets off the embryo's skeleton-forming circuitry, a genetic pathway absent in the starfish embryo. But because the otx enhancer is missing t-brain, the sea urchin must also rely on a different transcription factor to get the otx gene in the five-gene circuitry to kick in.
Meanwhile the t-brain binding site on the starfish's otx enhancer keeps otx focused on genes for the incipient gut. Davidson thinks that ancestral echinoderms had a t-brain site on the enhancer for otx, one that disappeared from that enhancer in the sea urchin. "This looks like species-specific jury-rigging," he points out. "The evolution of body plans happens by changes in the network architecture". [all typos are mine]
While changes in hox genes may be influential, there is also the enhancement and changes in expression of those hox genes. It is a very dynamic and ever changing phenomena. I just happened to have that issue of Science handy, but it is well worth the read if you happen to be in a library any time soon. It is heavy reading, so you might want to have a genetics text handy as well.

This message is a reply to:
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