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.
Yup.
I remember the good old days, in one of my past lives, riding beside Khan across the open steppe, killing the men and children and raping the women. Those were the days when a haunch of meat was a haunch of meat and a good weapon bought more glory than a handful of gold.
And probably at least a screwdriver
Yes!!
And not a time for dogmatism and thinking everything is known. Just the opposite.
Ahhh, yes.
Kids today just don't know about life!
Chimps aren't monkeys. A little light on basic information, aren't you pal
Sheeesh!
Depends on how far back you want to go to consider it "from scratch" :)
In any case, the suggestion that DNA does not have enough "information" to make a human being is silly on its face - a single set of chromosomes building a human being happens daily, and culminates every time a woman gives birth. Unless, that is, we want to posit the existence of uterine elves or fallopian angels, or some other invisible entity that sets out to build a baby.
A great number of things in the human body are essentially self-organizing according to the 'rules' set up by DNA - life is an emergent system.
Indeed, which is why, despite its popularity, to compare DNA to a computer program, is really quite an inapt analogy.
I assume. :)
Good for you, hobbies are nice things to have.
"and the amount of data needed to build a human body is simply not contained in DNA. DNA appears to be to the human body as "screen properties choices" is to a PC."
This rather a bold assertion to make. Just how much 'data' is needed to produce a human body and how much 'data' does the human genome have in comparison.
The analogies made about the genome being a blueprint or a computer program are insufficient to describe the chemical processes and their interactions, making the analogies nothing more than poor tools to help our visualization process.
The genome is definitely not a blueprint but it may be viewed as a set of interlocking algorithms much like a computer program or recipe.
In this model, poor as it is, the genome is a set of algorithms that produce complex systems out of available raw materials. The size of the genome has less to do with the resulting output than does the way the algorithms are written. It is possible when writing computer programs to make remarkably small pieces of code produce magnificently complex outputs.
I learned this little nugget while porting a 'Plant Fractal Generator' from SGI Unix to Mac OS during my work towards a B.Sc. in Computer Science. Before I returned to school to get that B.Sc. I spent 3 years producing material takeoffs from blueprints for a lumber yard which catered to a number of home builders.
Here?
Surely you jest.;-)
If you say so. However, the "forces of evolution" are observable and have been observed. Also, it is as easy to deny the existence of "macro-gravity" as it is to deny the existence of "macro-evolution". And such denial has equal impact upon the reality of both.
"I make this point because I'm into math and computer science and the amount of data needed to build a human body is simply not contained in DNA. DNA appears to be to the human body as "screen properties choices" is to a PC."
Is there enough in a monkey?
Is there enough in a dog?
Is there enough in a sperm + egg?
Is there enough in a plant?
Is there enough in an amoeba?
Is there enough in a bacterium?
Is there enough in a virus?
Millions of women will get pregnant tonight (heh, heh, heh :)) and produce a new human in 9 months.
Where do babies come from?
I try to refrain from personal attacks, but the above comment really deserves one.
Well, maybe not here, but presumably the people I linked to at Oak Ridge have taken that into account :)
I agree with you that chimpanzees are intelligent. But as you described, their behavior generally involves activities which will sustain life.
Wasn't "Fallopian Angels" a television program in the seventies?
Nothing personal, but this doesn't make any sense.
Huh? What doesn't make sense? That a gene is a DNA sequence that has a product (not necessarily being a protein)? Why does this not make sense to you? Here's the definition of a gene from a randomly chosen glossary. This one from the Human Genome Project. (emphasis added)
Gene: The fundamental physical and functional unit of heredity. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product (i.e., a protein or RNA molecule).
And the Dictionary of Cell and Molecular Biology gives the following definition for "Non-coding DNA":
DNA that does not code for part of a polypeptide chain or RNA. This includes introns and pseudogenes. In eukaryotes the majority of the DNA is non-coding. Non-coding strand refers to the so-called nonsense strand, as opposed to the sense strand which is actually translated into mRNA.
Now granted you CAN find some dictionaries or glossaries that refer to genes and/or coding regions as coding proteins only, but this distinction is obviously arbitrary and nonfundamental since the code itself, the structure of the gene itself, and the transcription mechanism, is no different between a gene that codes (ultimately) for a protein and one that codes for regulatory RNA.
But if you want to structure your argument solely on semantics, then fine. We'll draw the appropriate conclusions.
The 'intelligent designer' flies by and drops them in knapsack down your chimney!
It just doesn't make sense what you wrote.
You are quite correct. That is why no-one thinks the genome is just 'data'.
The genome isn't a 'list' of all the parts of the body. It an instruction set that can be arranged in multiple ways that describes how to build the body from raw materials. There is no one to one mapping of a gene to a feature, many genes will perform multiple functions and many functions are spread out between multiple genes.
Have you ever written a method/procedure/function that produces different outputs based on not just value but type of input? Have you ever written a function that takes another function as an input? If you have then you should realize how varied an output a function can produce just based on its input.
Now take those functions mentioned above and reduce them to nothing more than algorithms that can be applied to chemical interactions, taking into consideration of course those chemical's natural tendencies when in close proximity. The natural tendencies of chemical reactions reduces the number and size of the algorithms necessary to produce a specific result. This means that the genome is just a part of the 'recipe' (a recipe is just a set of algorithms and a list of raw materials) for a living organism.
During the construction of the organism, the recipe (DNA) not only relies on it's own algorithms and material lists but on the environments algorithms and lists. (Remember that the algorithms are written in terms of chemical reactions). In the case of humans, who are mammals of course, the developmental environment includes the mother, whose body is busy supplying raw materials and additional algorithms and inputs to augment those in the developing zygote.
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