Scientists Find Fingerprint Of Evolution Across The Human Genome

The Human Genome Project revealed that only a small fraction of the 3 billion “letter” DNA code actually instructs cells to manufacture proteins, the workhorses of most life processes. This has raised the question of what the remaining part of the human genome does. How much of the rest performs other biological functions, and how much is merely residue of prior genetic events?

Scientists from Cold Spring Harbor Laboratory (CSHL) and the University of Chicago now report that one of the steps in turning genetic information into proteins leaves genetic fingerprints, even on regions of the DNA that are not involved in coding for the final protein. They estimate that such fingerprints affect at least a third of the genome, suggesting that while most DNA does not code for proteins, much of it is nonetheless biologically important – important enough, that is, to persist during evolution.

To gauge how critical a particular stretch of DNA is, biologists often look at the detailed sequence of “letters” it consists of, and compare it with a corresponding stretch in related creatures like mice. If the stretch serves no purpose, the thinking goes, the two sequences will differ because of numerous mutations since the two species last shared an ancestor. In contrast, it’s believed that the sequences of important genes will be similar, or “conserved,” in different species, because animals with mutations in these genes did not survive. Biologists therefore regard conserved sequences as a sign of biological importance.

To test for conservation, researchers need to find matching stretches in the two species. This is relatively easy for stretches that “code” for proteins, where scientists long ago learned the meaning of the sequence. For “noncoding” regions, however, the comparison is often ambiguous. Even within a gene, stretches of DNA that code for pieces of the target protein are usually interspersed with much larger noncoding stretches, called introns, that are removed from the RNA working copy of the DNA before the protein is made.

Previous researchers assumed that mutations in the middle of introns do not affect the final protein, so they simply accumulate. In the new work, however, the researchers found signs that evolution rejects some types of mutations even in these regions of the genome. Although the selection is weak, “introns are not neutral,” in their effect on survival, says CSHL professor Michael Zhang, a bioinformatics expert who headed the research team.

To look for selection, CSHL researcher Chaolin Zhang, a doctoral candidate at Stony Brook University, looked in the human genome for a subtle statistical imbalance in how often various “letters” appear. The researchers attribute this imbalance to special short stretches of DNA that mark regions to be removed. Unless these signal sequences are sprinkled throughout an intron, the data suggest, it may not be properly spliced out, with potentially fatal consequences. Other sequences must likewise be preserved in the regions to be retained.

The scientists found a preference for some “letters” across intron regions, and the opposite preference in coding regions. Together, these regions make up at least a third of the genome, which is thus under selective pressure during evolution. The result supports other recent studies that suggest that, although most DNA does not code for proteins, much of it is nonetheless biologically important.

In addition to demonstrating how splicing affects genetic evolution, the statistical analysis identified possible signaling sequences, some that were already known and others that are new. According to co-author Adrian Krainer, a CSHL professor and splicing expert, “the exciting thing will be to experimentally test whether these predicted elements are really true.”

“RNA landscape of evolution for optimal exon and intron discrimination” appears in the April 15, 2008 edition of the Proceedings of the National Academy of Sciences. The paper is available online at http://www.pnas.org_cgi_doi_10.1073_pnas.0801692105.

Physorg ^ | 4-8-2008 | National Academy of Sciences

Try "National Academy of Imbeciles"

What kind of idiot continues to cling to the thoroughly debunked, sloppily concocted myth of "evolution"? There is absolutely no scientific evidence upon which might rest such a hairbrained theory. None.

Just goes to show, those who believe in nothing will pretty much believe in anything. Rather than admit the truth, they feverishly seek only that which their itching ears want to hear.

The price to be paid for insisting on a seat at this show just isn't worth it. Not by half.

{Hint} Forget the sunscreen... bring some barbecue sauce.

;-/

Try "National Academy of Imbeciles"

So your religious belief makes you smarter than some of the best scientists in the country? Or did you just stay a couple of nights in a Holiday Inn Express?

False. The theory of evolution is only "thoroughly debunked" to those who ignore science and wrap themselves in an extremely narrow interpretation of religion.

And false again. There is a huge amount of scientific evidence supporting the theory of evolution. I have personally seen a lot of the evidence for evolution during six years of grad school in which I studied fossil man, evolution, osteology and related subjects.

Just goes to show, those who believe in nothing will pretty much believe in anything. Rather than admit the truth, they feverishly seek only that which their itching ears want to hear.

False again. (Although that may be a self portrait for creationism.) There is a lot of evidence for the theory of evolution if one would just look.

The price to be paid for insisting on a seat at this show just isn't worth it. Not by half.

{Hint} Forget the sunscreen... bring some barbecue sauce.

Oh, so those of us who are convinced by the evidence for evolution are headed straight to hell?

Son, you are acting like a jerk. You are a very poor representative of your religion.

Usually, even a non-Christian knows something about the heavens, and the other elements of the world, about the motion and orbit of the stars and even their size and relative positions, about the predictable eclipses of the sun and the moon, the cycles of the years and the seasons, about the kinds of animals, shrubs, stones, and so forth, and this knowledge he holds to be certain from reason and experience. Now it is a disgraceful and dangerous thing for an infidel to hear a Christian, presumably giving the meaning of Holy Scripture, talking nonsense on these topics; and we should take all means to prevent such an embarrassing situation, in which people show up vast ignorance in a Christian and laugh it to scorn. The shame is not so much that an ignorant individual is derided, but that people outside the household of faith think our sacred writers held such opinions and, to the great loss of those for whose salvation we toil, the writers of our Scripture are criticized and rejected as unlearned men. If they find a Christian mistaken in a field which they themselves know well and they hear him maintaining his foolish opinions about our books, how are they going to believe those books in matters concerning the resurrection of the dead, the hope of eternal life, and the kingdom of heaven, when they think their pages are full of falsehoods on facts which they themselves have learnt from experience and the light of reason? Reckless and incompetent expounders of Holy Scripture bring untold trouble and sorrow on their wiser brethren when they are caught in one of their mischievous false opinions and are taken to task by those who are not bound by the authority of our sacred books. For then, to defend their utterly foolish and obviously untrue statements, they will try to call upon Holy Scripture for proof and even recite from memory many passages which they think support their position, although they understand neither what they say nor the things about which they make confident assertions [quoting 1Ti. 1:7].
St. Augustine, The Literal Meaning of Genesis, 1:42-43.

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