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.
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Nor, oddly enough, any scripture that says Tide gets the dirt out.
Eugenics (the practice of selective breeding in humans) predates both Hitler and Darwin.
Yeah. Basically none except the PRODUCT, whether for instance tRNA (leading to a protein) or just RNA. If the DNA sequence codes for a product then it's a gene, and a gene is a coding sequence by definition.
Not only preceeded Darwin, but suggested natural selection.
Does that mean that only 20 letters of DNA code seperate chickens from humans?
Compared to what happens in the development of a human brain from a single cell from the perspective of DNA, it's a fair comparison if you think about it. We've spent how many billions fo dollars trying to understand and cure poverity, and more than 30 years, and there too the comparison to a child poking at a worm is pretty fair. Just because a lot of well paid people are working on a problem and have a lot of terminology to discuss the problem doesn't mean the problem is almost understood.
"Does that mean that only 20 letters of DNA code seperate chickens from humans?"
Not if your a liberal.
Then there's no difference.
As with gravity, just because everything isn't understood doesn't mean the sun revolves around the earth.
There are multiple levels to the evolution debate. On one hand, those pushing for classroom changes want to deny an old earth and common descent; on the other hand, the most qualified evolution critics, such as Behe and Dembski, accept those as given.
I believe they were talking about just a couple of genes, not the whole genome. Otherwise this chicken hot dog I'm eating wouldn't taste as good.
Qualified by who? Qualified by being the most agreeable to evolution? Qualified as throwing out the bible? You can have them and their "qualifications".
By the way, I wouldn't dream of changing the classrooms in public schools/churches. I just don't let my kids go to those schools/churches. I don't try to change what other religions are doing, I try to get people out of their false religions.
Your solution is fine with me.
Indeed. And genocide has an even older, more lamentable pedigree, alas.
I think you would have to specify the sex of the compared humans. The Y chromosome contains ~51,000,000 bases and the X contains about ~153,000,000, making the difference (in number of bases) between a male and a female of about 1.5%.
Well, prepare to be ticked off quite a bit, then. Humans are animals, whether you like it or not. We are mammals (which are animals); we are primates (which are animals). We eat, breathe, and procreate just like other animals. We share large chunks of our DNA with animals. There is nothing in kind that separates us from other animals. Any differences are simply in degree.
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