Posted on 08/16/2006 11:38:54 AM PDT by PatrickHenry
One of the fastest-evolving pieces of DNA in the human genome is a gene linked to brain development, according to findings by an international team of researchers published in the Aug. 17 issue of the journal Nature.
In a computer-based search for pieces of DNA that have undergone the most change since the ancestors of humans and chimps diverged, "Human Accelerated Region 1" or HAR1, was a clear standout, said lead author Katie Pollard, assistant professor at the UC Davis Genome Center and the Department of Statistics.
"It's evolving incredibly rapidly," Pollard said. "It's really an extreme case."
As a postdoctoral researcher in the lab of David Haussler at UC Santa Cruz, Pollard first scanned the chimpanzee genome for stretches of DNA that were highly similar between chimpanzees, mice and rats. Then she compared those regions between chimpanzees and humans, looking for the DNA that, presumably, makes a big difference between other animals and ourselves.
HAR1 has only two changes in its 118 letters of DNA code between chimpanzees and chickens. But in the roughly five million years since we shared an ancestor with the chimpanzees, 18 of the 118 letters that make up HAR1 in the human genome have changed.
Experiments led by Sofie Salama at UC Santa Cruz showed that HAR1 is part of two overlapping genes, named HAR1F and HAR1R. Evidence suggests that neither gene produces a protein, but the RNA produced by the HAR1 sequence probably has its own function. Most of the other genes identified by the study also fall outside protein-coding regions, Pollard said.
Structurally, the HAR1 RNA appears to form a stable structure made up of a series of helices. The shapes of human and chimpanzee HAR1 RNA molecules are significantly different, the researchers found.
RNA is usually thought of as an intermediate step in translating DNA into protein. But scientists have begun to realize that some pieces of RNA can have their own direct effects, especially in controlling other genes.
The proteins of humans and chimps are very similar to each other, but are put together in different ways, Pollard said. Differences in how, when and where genes are turned on likely give rise to many of the physical differences between humans and other primates.
Researchers at UC Santa Cruz, the University of Brussels, Belgium and University Claude Bernard in Lyon, France, showed that HAR1F is active during a critical stage in development of the cerebral cortex, a much more complicated structure in humans than in apes and monkeys. The researchers found HAR1F RNA associated with a protein called reelin in the cortex of embryos early in development. The same pattern of expression is found in both humans and rhesus monkeys, but since the human HAR1F has a unique structure, it may act in a slightly different way. Those differences may explain some of the differences between a human and chimp brain.
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The chimpanzee genome was published in Nature in 2005, showing that the DNA sequences of humans and chimps are more than 98 percent identical. The current work was funded by the Howard Hughes Medical Institute, the U.S. National Institutes of Health and other agencies.
http://home.wxs.nl/~gkorthof/
I like that site a lot. Without it I might not have known that Michael Denton, author of "Evolution, A Theory In Crisis," has done a complete 180 and accepts the naturalistic version of evolution without reservation.
You don't hear Denton's name mentioned much among creationists these days.
Some people like to assert that minds are never changed in these debates, but Denton is proof that it happens. It is also worth mentioning that Behe, the reining guru of Intelligent Design, is on record as accepting common descent, and so is the webmaster for Dembski's site.
Deliberate ignorance is such a sad thing to witness.
Deputies in the lower House, Senators in the Upper.
Uh, "wrong"? How about incomplete? Good old fashioned population genetics, as with much else that came out of the neodarwinian synthesis, is still valid and highly useful. Are you saying that the application of rigorous mathematical models to population biology was basically wrong headed? Should we just throw out, for instance, the work of Sewall Wright and R. A. Fisher? (Remembering that much of Fisher's work, in particular, was applicable in other areas of science besides biology, and included fundamental contributions to mathematics, statistics, as well.)
It seems to me that this is like saying that Galileo's principal of inertia is "wrong" just because Newton, and then Einstein, came up with more inclusive laws of motion.
Transitions at most taxonomic levels detailed here. From that link, for instance:
Early ungulates and early carnivores compared. The link says of this figure, "Moving further up the taxonomic hierarchy, the condylarths and primitive carnivores (creodonts, miacids) are very similar to each other in morphology (Fig. 9, 10), and some taxa have had their assignments to these orders changed."
That's how evolution really works. There are no jumps. It's a branching tree structure of divergence.
The polymorphisms between Chimp, Human, and mice do not follow a continuum, as would be more expected in terms of differences, as do classical, ie protein coding, genes.
Tools are fine.
But wrong. Not incomplete, wrong.
It seems to me that this is like saying that Galileo's principal of inertia is "wrong" just because Newton, and then Einstein, came up with more inclusive laws of motion.
Analogy doesn't hold up.
Watch this space -- I've heard (from my wife, the biologist in the family) that this is emerging as a key area of research.
I've been seeing more and more articles on this very subject. 'Junk' DNA was tought, for a long time, to be any non-protien encoding DNA. Now, we are learning that some sections of DNA code for RNA that does not trnaslate into proteins, but that this RNA functions in a regulatory role. It is also very interesting that these regulating genes seem to have very strong sensitivity towards functionality and development. This study indicates just that. The areas of greatest difference between humans and chimps, but are very similar between chimps and other mammals are not protein encoding. That implies the regulatory functions are far mor important for the development of a living thing. I guess it could be though of like this. Protien coding DNA tells you what building blocks to construct, and the regulatory DNA tells you how to put them together. It sounds very exciting!
And by extension, not much difference between Dems and chickens:
Figure 10. Comparison of skulls of the early ungulates (condylarths) and carnivores. (A) The condylarth Phenacodus possessed large canines as well as cheek teeth partially adapted for herbivory. (B) The carnivore-like condylarth Mesonyx. The early Eocene creodonts (C) Oxyaena and (D) Sinopa were primitive carnivores apparently unrelated to any modern forms. (E) The Eocene Vulpavus is a representative of the miacids which probably was ancestral to all living carnivore groups. (From Vertebrate Paleontology by Alfred Sherwood Romer published by The University of Chicago Press, copyright © 1945, 1966 by The University of Chicago. All rights reserved. This material may be used and shared with the fair-use provisions of US copyright law, and it may be archived and redistributed in electronic form, provided that this entire notice, including copyright information, is carried and provided that the University of Chicago Press is notified and no fee is charged for access. Archiving, redistribution, or republication of this text on other terms, in any medium, requires both the consent of the authors and the University of Chicago Press.)
Um, no. These are genes. These are coding regions, and recognizable as such. Nothing that recognizably codes RNA (whether or not that RNA goes on to code proteins) has been referred to as "junk DNA".
Yes, but there is a big difference between showing a relationship between a gene and extracellular development and having any understanding of how it works. So they, scientists, find a way to apply a stimulus to a piece of DNA and can measure a result. But to advertise this as some kind of proof of evolution or tout it as some understanding beyond a child poking at a worm is to try to convince the general public that "science" knows things that it doesn't know at all.
Your 71 proves my point.
This study would therefore, given your reasoning, show that chimps are closer to mice than humans.
What will happen is that the vehicle for speciation will change from genes to various repeat elements such as this and their distributions and relative conservations between species will be used rather than gene/protein comparisons.
This though is much more difficult because it is a much grander scale and lots of full genome sequences for many organisms must be known to be used for input.
Ofcourse they do, my point was about the lack of understanding about how these relationships work. See previous post.
Uh, no, I put genes in quotes to indicate the issue is of interest.
In this case you are wrong, they are not coding sequences but they are transcribed.
Do you know the difference?
If you do your post I am replying to was odd for you to make.
Look, don't be an idiot.
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