Scientists Find Fingerprint Of Evolution Across The Human Genome

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

[blam]

Scientists find a 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.

Conservation of genetic information

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.

Signs of splicing

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.

Source: Cold Spring Harbor Laboratory

[Citizen Tom Paine]

Humans are still evolving. The species is becoming more gracile. There have been recent mutations in some to increase intelligence. Needless to say these were not trumpeted in the MSP.

Do not assume that the epitome of evolution is Homo sapien. I suspect that Mother Nature still has some tricks up her sleeve.

[allmendream]

And this is the most common mistake of strawman evolution.

They think evolution denotes advancement. Every year everything gets better stronger faster more disease resistant etc. This is crap.

Every year the animals become more adapted to a CHANGING environment, some years it pays to be slimmer and faster, other years it pays to be fatter and slower but healthier. There is no such thing as a free lunch. In Biology the concept is known as antagonistic pleotropy.

Thinking that evolution denotes advancement, and assuming that humans are the end all be all (a delusion I do not labor under), they thus conclude “if evolution were true all plants and animals would have turned into humans”.

[RobRoy]

>>The Creation Weenies are gonna be in here any second to give you a wedgie!<<

You need to hold off on the ad-hominem until you can aim at specific targets.

We have rules, you know!

[RobRoy]

The facts in this article are undeniable.

The conclusions, less so...

[Dmitry Vukicevich]

The Creation Weenies as oppossed to Evolutionist Morons?

And so the Evolutionist Circle Jerk continues “we are smart and let us tell you why.”