Freethought & Rationalism Archive

Oolon Colluphid · 02-22-2002, 02:39 AM

Following on from the thread a while back (which I can’t spot atm) about the genetics of arthropod bodyplan evolution, here’s some more from the current issue of Nature:

Quote:

Nature 415, 914 - 917 (2002)

Hox protein mutation and macroevolution of the insect body plan

Matthew Ronshaugen, Nadine McGinnis & William McGinnis

A fascinating question in biology is how molecular changes in developmental pathways lead to macroevolutionary changes in morphology. Mutations in homeotic (Hox) genes have long been suggested as potential causes of morphological evolution, and there is abundant evidence that some changes in Hox expression patterns correlate with transitions in animal axial pattern. A major morphological transition in metazoans occurred about 400 million years ago, when six-legged insects diverged from crustacean-like arthropod ancestors with multiple limbs. In Drosophila melanogaster and other insects, the Ultrabithorax (Ubx) and abdominal A (AbdA, also abd-A) Hox proteins are expressed largely in the abdominal segments, where they can suppress thoracic leg development during embryogenesis. In a branchiopod crustacean, Ubx/AbdA proteins are expressed in both thorax and abdomen, including the limb primordia, but do not repress limbs. Previous studies led us to propose that gain and loss of transcriptional activation and repression functions in Hox proteins was a plausible mechanism to diversify morphology during animal evolution. Here we show that naturally selected alteration of the Ubx protein is linked to the evolutionary transition to hexapod limb pattern.

and

Quote:

Nature 415, 910 - 913 (2002)

Evolution of a transcriptional repression domain in an insect Hox protein

Ron Galant and Sean B Carroll

Homeotic (Hox) genes code for principal transcriptional regulators of animal body regionalization. The duplication and divergence of Hox genes, changes in their regulation, and changes in the regulation of Hox target genes have all been implicated in the evolution of animal diversity. It is not known whether Hox proteins have also acquired new activities during the evolution of specific lineages. Amino-acid sequences outside the DNA-binding homeodomains of Hox orthologues diverge significantly. These sequence differences may be neutral with respect to protein function, or they could be involved in the functional divergence of Hox proteins and the evolutionary diversification of animals. Here, we identify a transcriptional repression domain in the carboxy-terminal region of the Drosophila Ultrabithorax (Ubx) protein. This domain is highly conserved among Ubx orthologues in other insects, but is absent from Ubx in other arthropods and onychophorans. The evolution of this domain may have facilitated the greater morphological diversification of posterior thoracic and anterior abdominal segments characteristic of modern insects.

I wish I understood these well enough to turn it too our advantage

Oolon

scigirl · 02-23-2002, 10:34 AM

Oolon--

When that journal eventually lands on my desk at work, I'll read that article. Hopefully it will have one of those nice "layman's summaries," and i'll put it here.

HOX genes are great evidence for evolution. Except you have to understand gene patterning and gene expression to accept the evidence, and you can guess how many YECS do either of these things. . .

scigirl

StrongMan · 02-23-2002, 10:39 AM

Is that the same as <a href="http://ucsdnews.ucsd.edu/newsrel/science/mchox.htm" target="_blank">this</a>?

lpetrich · 02-23-2002, 07:03 PM

Quote:

Originally posted by jcgr81:
<strong>Is that the same as <a href="http://ucsdnews.ucsd.edu/newsrel/science/mchox.htm" target="_blank">this</a>?</strong>

Yes, that's absolutely right.

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02-23-2002, 10:34 AM	#2
scigirl Veteran Member Join Date: Jul 2001 Location: Seattle Posts: 4,261	Oolon-- When that journal eventually lands on my desk at work, I'll read that article. Hopefully it will have one of those nice "layman's summaries," and i'll put it here. HOX genes are great evidence for evolution. Except you have to understand gene patterning and gene expression to accept the evidence, and you can guess how many YECS do either of these things. . . scigirl

02-23-2002, 10:39 AM	#3
StrongMan Regular Member Join Date: Mar 2001 Location: Bumblefuck Posts: 488	Is that the same as <a href="http://ucsdnews.ucsd.edu/newsrel/science/mchox.htm" target="_blank">this</a>?

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