Posted on 03/29/2006 1:47:22 PM PST by SampleMan
Spirals of DNA, once thought to be merely the passive memory banks that preserve life’s blueprints, may also actively modify themselves under certain conditions, according to Princeton University scientists.
A team of molecular biologists has found that some single strands of DNA are capable of removing a genetic building block from the spiral, a task previously thought to be impossible without the involvement of a separate catalyst such as RNA or proteins. Such removal, called depurination, occurs only at a single point within a particular genetic sequence, one that appears at least 50,000 times in the human genome. The team’s discovery that the removal occurs consistently in laboratory samples indicates that DNA is a more dynamic substance than was previously thought, and it raises the possibility that other unexpected behaviors still await discovery in this well-studied molecule.
“No one ever dreamed genomic DNA may have another function besides memory storage, but it apparently does,” said Jacques Fresco, the Damon B. Pfeiffer Professor in the Life Sciences at Princeton. “We don’t really know yet why or how it happens, but it makes us wonder what else DNA might be doing without our knowledge.”
Dr. Ann Skalka, senior vice president for basic science at the Fox Chase Cancer Center in Philadelphia, said the findings merit continued attention.
“This fascinating and unanticipated new property of DNA has the potential to cause substantial damage to our cells, leading to cancer or other diseases, unless it is controlled or exploited for some beneficial purpose,” she said. “We will stay tuned.”
Fresco’s team published its findings in the March 21 issue of the journal, Proceedings of the National Academy of Sciences. Also contributing to the research are Princeton researcher Olga A. Amosova and Richard Coulter, currently at West Chester University.
The double-stranded helical structure of DNA is a shape familiar to many, and these long, stringy molecules are in most circumstances unchanging and highly stable -- valuable characteristics for objects whose function is to preserve the master plan of the organism that carries them. Altering the sequence of a DNA strand is often necessary for innumerable bodily functions, such as growth and healing, but scientists previously thought that such alterations require other chemical catalysts or enzymes to do the clipping and rearranging.
When DNA does undergo such changes, its two strands sometimes separate from one another like a broken zipper splitting down the middle, the teeth of one side pulling away from the other. But in some cases, each side will then often bunch up so its teeth can latch on to others from the same side, forming small “loops” of a single-stranded DNA that extend out from the side of the double-stranded helix’s “stem.”
“For genes to express themselves and create change within the body, you absolutely have to get the two strands of DNA apart first, and it’s only through separation that DNA forms these stem-loops,” said Amosova, a research molecular biologist and Fresco’s long time collaborator. “Such separation occurs, for example, when genes are doing something to regulate the body.”
But the team found that if a stem-loop forms from a particular sequence of DNA, one of the genetic “teeth” will fall spontaneously from that side of the zipper, and the weakened strand will eventually break apart in that spot unless it is repaired by enzymes in the cell. Fresco said this sort of activity seems akin to self-mutilation at first glance.
“To a scientist, this kind of self-inflicted genetic damage appears unhealthy, the sort of thing that would cause undesirable mutations and could kill off the organism,” Fresco said. “Cells have evolved a complex DNA repair system to constantly repair such damage. But evolution has not, as we’d expect, put a stop to it. So we theorize it must be happening for some good reason that we have yet to uncover.”
Of the more than 3 billion DNA building blocks in the human genome, the 18-residue sequence that gives rise to the cleavage occurs in about 50,000 places -- a very significant number, Fresco said.
“We can only speculate now as to what aspects of biology this self-cleavage could influence, but the general function of stem-loops combined with the number of sites where depurination can occur does make us curious enough to look further,” Amosova said. “Such a self-depurination capability may, for example, be beneficial in sections of the genome involved in antibody production, where losing a building block from the sequence could lead to higher mutation rates in the antibody-coding genes. This, in turn, could lead to a larger variety of antibodies to protect the body more effectively.”
More generally, Amosova said, losing a building block increases the flexibility of the otherwise highly rigid DNA molecule, which in some circumstances needs to be bent.
“Flexibility could help with DNA packaging, which happens any time you need to stuff DNA into a tight place,” she said. “In particular, viruses typically pack a lot of DNA strands into their shells, leaving virtually no space unused. It may also play a role in the folding of DNA in chromosomes.”
Still, Fresco said, it remains too early to tell where the discovery will lead, though the team will look for some possible biological role for their finding.
“Thus far we have observed this effect under laboratory conditions that closely resemble those within the cell. Now, we would like to observe them directly in the cell nucleus,” he said. “If we have indeed found one way that DNA can change itself spontaneously, there might be others, and we plan to hunt for them.
“Additionally, I might mention that this discovery was made while we were exploring ways to repair the genetic mutation that causes sickle cell anemia,” Fresco said. “We noticed that the depurination occurs right next to the site of the mutation responsible for the disease, but we don’t yet know if there’s any relation between these two facts. We certainly hope we’ve noticed an effect that will eventually offer some new approaches to many diseases.”
And why exactly am I a "troll". I have been on FR for some time. I post regularly.
What was it about this article that you found to be an afront? Have you even commented on the article, or just the heretics?
I found the article interesting and a possible connection to what I find lacking in the understanding of evolution. An explanation of mutation, as I think it likely occurs. You are certainly free to disagree, but you won't get there by simply calling me a troll.
I started out by amusingly noting that my post would stir up a hornets nest of people denouncing ID, whether ID was present or not. I was absolutely correct.
Reminds me of the man who got stoned to death for telling a crowd that they were uncivil. They showed him.
I'm rubber, you're glue. Now go and read the article and argue with Princeton.
Who knows? It's not interesting enough to pursue.
I started out by amusingly noting that my post would stir up a hornets nest of people denouncing ID, whether ID was present or not. I was absolutely correct.
That constitutes a confession of trolling. Not that there's anything wrong with that (IMHO), mind you...but you can at least spare us the dudgeon over the accusation.
"I'm rubber, you're glue. Now go and read the article and argue with Princeton."
How about instead you provide:
1) A post where I told someone to shut up
2) Any scientists who has ever said that everything there is to know about evolution is already known.
While I've singlehandedly had you all tied down tilting at my windmill, the IDers have staged a coup and taken over the country's biology departments. You're doomed.
If you want to know why reasonable people think evolutionists are incapable of discussing evolution without venom, look no further than yourselves.
On many occasions I've joined a thread about evolution to try to add what I think is a perplexing issue concerning mutation. One or all of you have been tripwired to attack. Although I have never pushed ID (and have repeatedly said that I don't feel ID is necessary to justify my faith), you feel free to attack me and/or my religion. You are a bunch of self-righteous hacks that can't stand anyone discussing something that you think is incorrect. In short, you're the type that no one wants to sit next to at the bar.
I've stated repeatedly that I believe that evolution occurs, and repeatedly been told that I'm a liar with a not so secret ID agenda. I've been told that my ideas on mutation couldn't possibly be correct and that I'm an idiot.
So you all got your panties in a wad because I said you weren't open to new ideas. What's funny is that I simply posted the "rabid dog" sign, you all ran and stood under it.
How about instead you provide:
1) A post where I told someone to shut up
2) Any scientists who has ever said that everything there is to know about evolution is already known.
"Why did you double-post the nylon bug?"
Kill it before it multiplies!!!!
I can go on any thread and post strawman arguments and/or just lie say things less that true (remember Freepspeak) about things.
Such things just makes one an a$$hole -- not nearly as clever as you think you are.
"All recognized scientists agree on the general TToE.
Let me guess as to how one goes about getting unrecognized."
Sign up again as Unrecognized Scientist?
Step one: Troll makes outrageous, unsupportable statement about scientists and Kool-Aid. (post 1)
Step two: Someone asks for verification.
Step three: Troll dodges by making reference to some earlier thread. (post 10)
Step four: Someone else asks for verification.
Step five: Troll dodges again. (post 36)
Step six: Another person asks for verification.
Step seven: Troll dodges again, mentions cold fusion. (post 38)
Step eight: Troll claims his "rabid" opposition is amusing. (post 42)
Step nine: Troll dodges accusation that he made up his original statement, tells poster to stay focused. (post 45)
Step ten: Troll accuse a poster of improper behavior, without providing evidence. (Post 51)
Step eleven: Etc., etc., etc. [Continue until thread is moved to Smokey Backroom, at which point you've won.]
They come in "pairs".
Aw, shucks, now they will all know how to do it!
"We don't even fully understand gravity."
We Really don't understand gravity.
http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html
A gravitational effect from electro-magnetism (spinning superconductor).
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