DNA question

[cosmik debris]

I've read several times lately that "60% or so of human DNA is actually virus DNA"

I suspect that this is a crock-o-shit, but I didn't want to enter a fight I can't win.

Can anyone here enlighten me on the origin of this thought and its credibility?

[trotsky]

1. Boy oh boy that's an interesting claim.

There's no doubt that virtually all animals have virus DNA - one example I have read concerns the great difficulty in pig-human transplants. Human immune systems have a VERY strong reaction to pig DNA in the organs, and the theory is that long ago our common ancestor faced a particularly nasty virus. The line that led to pigs fought the virus by incorporating its DNA and neutralizing it. Our line apparently developed a gene to attack it.

Hey - there's a thread on the JREF forum about it!
http://forums.randi.org/showthread.php?t=103034

Looks like the original claim (we have more than 50% DNA from viruses) was made in the NY Times so I guess it has some validity.

[TZ]

2. I would think that its really the other way around

that many viri have picked up mamammalian DNA from their travels. Remember that viri incorporate themselves into host DNA and mutate very quickly.
Also there are theories that some of our molecular structures came from bacteria and viri that were in symbiotic relationships.
But also remember that we share 99.9% of our genes with our closest relatives Chimpanzees and NO ONE is going to mistake a chimp for a human. So even though that sounds like alot 50-60% isn't as significant as it sounds.

[Warpy]

3. Actually, no.

What they originally dismissed as "junk DNA" in the human genome project has been discovered to be bits and pieces of ancient retroviruses.

They're now speculating that the evolutionary jumps are viral in nature.

They've never been able to explain the discontinuous nature of evolution and this is as good an explanation for the mechanism as any. In fact, it's something I've speculated on privately in the past.

It sure beats the hell out of getting seeded by alien DNA from UFOs and comets.

One really curious thing they've discovered is that the mechanism that attaches the fertilized blastocyst to the uterine wall in sheep is viral in origin, meaning that the jump from oviparous to viviparous was likely a viral one.

Science, like wingnuttery, is screwier and screwier the closer you look at it.

[enki23]

4. not sure about that percentage, or about "viral" but there's plenty of transposon DNA in there

check out the alu sequence, for instance, which is (all by itself) estimated to make up approximately 10% of the human genome. it shorter than a typical mobile DNA element (around 300 base pairs), and doesn't code for any functional proteins (or RNAs, though it is originally derived from a bit of functional RNA that makes up part of the signal recognition particle).

alu is cool, because it makes a really good marker for human and primate evolution. people (and primates in general) who share an alu insertion point are almost certain to share an ancestor, and we have up to a million (or more?) alu sites in our genomes. alu is a retrotransposon, meaning the DNA sequence gets transcribed to RNA, and then back again via the reverse transcriptase from some other (larger, coding) mobile element and the resulting DNA can insert itself into new places in the genome, sometimes leading to genetic diseases. many of the larger retrotransposons code for their own reverse transcriptases, and are very much like retroviruses in action

anyway, we've definitely got plenty of dna that's capable of acting virus-like, or was that way in the past, the retrotransposons being probably the most obvious example. that isn't the same thing, however, as saying it's "virus DNA". in any case, that statement is probably oversimplified, and exaggerated, but not entirely wrong.

[WoodrowFan]

5. I can think of a few

I can think of a few people who have a far greater percentage of their DNA from viruses...

[HamdenRice]

6. "I suspect that this is a crock-o-shit"--not a very scientific way of evaluating claims

Just because you "suspect" something isn't true doesn't mean it's a "crock-o-shit."

Any wingnut can "suspect" that evolution didn't happen and that man walked with dinosaurs.

When you learn that what you "suspect" is not how to evaluate claims -- that claims need to be evaluated against evidence -- then you will have taken a major step forward intellectually.

[cosmik debris]

7. You are stalking me!

[TZ]

8. what a surprise

Our local "watchdog" has to make sure we skeptics "behave properly" because you know HE is the expert on everything and anything.
First R/T now skeptics. I'm surprised he hasn't asked Skinner to create a forum for REAL skeptics because according to someone none of us here are...:eyes:

[cosmik debris]

9. He has really lost it in the

Healthscare Lounge.

He's complaining that I used the phrase "really makes much difference". And here he is complaining that I used the phrase crock-o-shit.

I think he is losing it.

[Ian David]

10. "Ignored" is stalking you? n/t

[cosmik debris]

11. He's become completely obsessed with teaching me a lesson

For my own good of course.

:rofl:

[TZ]

12. Yeah he was doing that to me

Apparantly he felt the need to teach me about MY field because of course he KNOWS a scientist and that beats my actual field experience..:crazy:

[cosmik debris]

13. I can't imagine how fragile his ego must be

to need so much self-reinforcement. But practically every one of his posts is about stroking his own ego.

[dropkickpa]

17. Heh heh

You said stroking.

[cosmik debris]

18. And you know what I was thinking! n/t

[muriel_volestrangler]

14. He asked for the origin of the claim, and its credibility

in the part of DU where you're most likely to get knowledgeable answers, without pointless sniping (well, most of the time ... :eyes: ). cosmik debris never claimed to have 'evaluated' this already; he said he wasn't going to argue about it without knowing more. Very sensible and reasonable, I'd say.

[Random_Australian]

21. Indeed! If I were to think something was a crock of shit, would I be content with that?

No! I'd try and get enough information to work out if the claim was true or not. I could ask scifinder, or if it is more laid back I'd ask a group of people that are likely to give me information on the subject. That would be especially useful for specific claims.

Wheeeee! That concludes today's lesson: Why your insults are completely unjustified III: Basic evaluation of another's method.

[Deep13]

15. Sounds pretty unlikely to me.

I would ask the person making that claim to substantiate it. If not, I would rely on the advice in my sig-line.

[salvorhardin]

16. The claim that over 50% of human DNA is comes from viruses is made in this NY Times article

Yet viruses have not only taken; they have also repaid us in ways we are just beginning to tally. “Viral elements are a large part of the genetic material of almost all organisms,” said Dr. Sharp, who won a Nobel Prize for elucidating details of our genetic code. Base for nucleic base, he said, “we humans are well over 50 percent viral.”

Scientists initially dismissed the viral elements in our chromosomes as so much tagalong “junk DNA.” But more recently some researchers have proposed that higher organisms have in fact co-opted viral genes and reworked them into the source code for major biological innovations, according to Luis P. Villarreal, director of the Center for Virus Research at the University of California, Irvine.
http://www.nytimes.com/2008/01/08/science/08angi.html?em&ex=1199941200&en=3bd96f63379d275d&ei=5087%0A

[TheWraith]

19. It's more accurate to say that humans and viruses share large chunks of DNA.

But then so do humans and every other single living thing on Earth. We've got a 98.4% commonality of DNA with chimpanzees, but that doesn't mean we're 98.4% chimp, or that chimps are 98.4% human. It means we've got a lot in common on a genetic level.

It's true that sometimes DNA held by viruses is integrated into the species that they prey upon--and vice versa. That's just the way it works.

[TZ]

20. Yep. Great explanation. n/t