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Identical Twins Not Identical After All

samzenpus posted more than 6 years ago | from the one-of-these-things-is-not-like-the-other dept.

Medicine 159

Hugh Pickens writes "Contrary to previous beliefs, identical twins are not genetically identical. Researchers studied 19 pairs of monozygotic, or identical, twins and found differences in copy number variation in DNA which occurs when a set of coding letters in DNA are missing, or when extra copies of segments of DNA are produced. In most cases, variation in the number of copies likely has no impact on health or development but in others, it may be one factor in the likelihood of developing a disease (pdf). "Those differences may point the way to better understanding of genetic diseases when we study so-called discordant monozygotic twins....a pair of twins where one twin has a disorder and the other does not," says Carl Bruder, Ph.D. "If twin A develops Parkinson's and twin B does not, the region of their genome where they show differences is a target for further investigation to discover the basic genetic underpinnings of the disease.""

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Identical twins are like Slashdot dupes (4, Funny)

Daimanta (1140543) | more than 6 years ago | (#22500022)

You think they are exactly the same, but they are always slighly different.

Re:Identical twins are like Slashdot dupes (4, Funny)

s74ng3r (963541) | more than 6 years ago | (#22500554)

You think they are exactly the same, but they are always slightly different.

Re:Identical twins are like Slashdot dupes (3, Funny)

Anonymous Coward | more than 6 years ago | (#22500590)

You think they are exactly the same, but they are always slightly diffenert.

Re:Identical twins are like Slashdot dupes (3, Funny)

Thanshin (1188877) | more than 6 years ago | (#22500852)

You think they are exactly the same, but they are always slightly diffenert.
The reader concludes the similarities between both are absolute; however, by a negligible disparity, that is not so.

Re:Identical twins are like Slashdot dupes (2, Interesting)

theaveng (1243528) | more than 6 years ago | (#22501218)

Well then.

That explains why Playboy's "Dalmer Triplets" have differing breast sizes. I thought I was just seeing things, but apparently there really IS a difference.

(ducking and running)

Re:Identical twins are like Slashdot dupes (1)

CFTM (513264) | more than 6 years ago | (#22502052)

Why duck and run? This seems like a perfectly legitimate scientific observation to me. After all, I too read Playboy for the articles!

Re:Identical twins are like Slashdot dupes (3, Funny)

Zencyde (850968) | more than 6 years ago | (#22502686)

Yeah? Well, I read Slashdot for the articles.

Re:Identical twins are like Slashdot dupes (4, Funny)

somersault (912633) | more than 6 years ago | (#22500854)

You think they are exactly the same, but they are always slyly different.

Re:Identical twins are like Slashdot dupes (0)

Anonymous Coward | more than 6 years ago | (#22501034)

yes but then again ignorance is bliss. they are slightly different for a reason, natural genetic repeating always has a mutation or two so why do this? i think that we evolved to have gene mutations for the reason that we can better prepare against a diease like Parkinson's which we have no cure. this may in fact lead to something more extraordinary such as the new and upcoming nano technology to repair and rid us of such diseases.

Re:Identical twins are like Slashdot dupes (0)

Anonymous Coward | more than 6 years ago | (#22501128)

Enter epigenetics, subby. Sad that more people don't know this. It's not exactly new.

Re:Identical twins are like Slashdot dupes (1)

randalny (227878) | more than 6 years ago | (#22502738)

Nova has already had a very good episode on the field of epigenetics:

http://www.pbs.org/wgbh/nova/genes/ [pbs.org]

The most remarkable concept in this field is that it is possible to INHERIT epigenetic traits from your parents or grandparents that they developed only in their lifetime.

It also brings into focus the dangers of chemicals like pesticides, in that they are often chemicals that cause DNA methylation. Thus it could be possible to pick up genetic problems from eating pesticides, then pass those problems along to your children and grandchildren.

Hell that makes it worse (4, Funny)

MosesJones (55544) | more than 6 years ago | (#22500030)

I'm sure we've all had that embarrassing occasion of going out with one twin, getting drunk and waking up with the other. It used to be okay to claim you were drunk and couldn't tell them apart, you'd still get a slap but not a knee in the groin... now they can be told apart using simple genetic testing there really is no excuse.

In other news the part of the movie industry targeted with making crap movies aimed at teenage boys was shut down as plot lines had become "medically unsupportable".

Re:Hell that makes it worse (5, Funny)

RuBLed (995686) | more than 6 years ago | (#22500098)

I'm sure we've all had...


Dude, you're still drunk... this is /. by the way.
Look behind you, that's your bed... and there are no twins...

Re:Hell that makes it worse (1)

TubeSteak (669689) | more than 6 years ago | (#22500666)

Look behind you, that's your bed... and there are no twins...
I'm sure she has a twin [nyud.net] (SFW Picture)
If there's one thing most /.'ers do not lack, it's food.

Re:Hell that makes it worse (1)

sorak (246725) | more than 6 years ago | (#22501606)

Look behind you, that's your bed... and there are no twins...

But, if he's drunk enough, then the Linux Torvalds poster over his bed may appear to be hot looking twins.

Re:Hell that makes it worse (0)

Anonymous Coward | more than 6 years ago | (#22500150)

In other news the part of the movie industry targeted with making crap movies aimed at teenage boys was shut down as plot lines had become "medically unsupportable".
What do you mean? Clearly this wholly explains all those evil twin plot lines. Oh teenage boys! Never mind.

Re:Hell that makes it worse (5, Funny)

cp.tar (871488) | more than 6 years ago | (#22500188)

Clearly this wholly explains all those evil twin plot lines.

Yeah, I've always wondered why it is that the evil twin has a pointy beard.

I'd never have thought that the cause was genetic.

Re:Hell that makes it worse (0)

edwardpickman (965122) | more than 6 years ago | (#22500704)

Nothing genetic about it the good one just shaves.

Re:Hell that makes it worse (2, Funny)

menkhaura (103150) | more than 6 years ago | (#22500796)

You must be a HIT at parties!

So.... (3, Funny)

Anonymous Coward | more than 6 years ago | (#22500032)

What gene difference made those twins so different (Danny de Vito and Arnold Schwarzenegger)

Wonder how this affects... (5, Interesting)

Anonymous Coward | more than 6 years ago | (#22500046)

...decades of experiments that assumed twins have identical DNA. One twin may not be such a good control after all...

Re:Wonder how this affects... (5, Interesting)

mrbluze (1034940) | more than 6 years ago | (#22500134)

...decades of experiments that assumed twins have identical DNA. One twin may not be such a good control after all...

Well experiments can prove an association of two events, or causation of an event on another. Twin studies show associations and the experimenters usually jump to causation in their discussion to make the paper interesting to read. So it doesn't invalidate the experiments but shows that in all of science we can never assume we have excluded all confounding.

Actually this finding isn't all that surprising. For example, Trisomy-21 (Down's Syndrome) has different severities depending on how far along the line the trisomy developed (how many cells existed when the trait was introduced). It shows that the genetic makeup within an individual is heterogenous, let alone between two 'identical' individuals. The genetic code in your left hand is likely to differ from that in your right hand by a (numerically) small degree.

However, if the genetic change is an important one, then it follows that your left hand might be very different from your right (eg: more hair on one than the other, or one side more likely to develop cancer, etc).

*AHEM* (5, Funny)

AlgorithMan (937244) | more than 6 years ago | (#22500424)

http://xkcd.com/263/ [xkcd.com]
;-)

Re:*AHEM* (1)

mrbluze (1034940) | more than 6 years ago | (#22500652)

Isn't mathematics a philosophy subject?

Re:*AHEM* (1)

somersault (912633) | more than 6 years ago | (#22500874)

Logic is, not sure about general maths.

Re:*AHEM* (1)

geminidomino (614729) | more than 6 years ago | (#22501458)

No, Math is math. Has it's own subheader. Logic appears under there, too, but the dedicated classes that are usually in the PHI section are usually rhetoric-centered.

Re:*AHEM* (1)

somersault (912633) | more than 6 years ago | (#22502396)

That's why I said 'general maths' and not just Maths. I don't think that they do much long division or integration in philosophy classes for example.

Re:Wonder how this affects... (5, Insightful)

JeffL (5070) | more than 6 years ago | (#22500408)

It doesn't have too much effect, really. MZ twins are similar on a trait because of genes that they share (traditionally, all of them) and environment they share (growing up in the same house, etc.) They are different on a trait due to environmental factors they don't share (such as going to different colleges) and error (measurement error in assessing the trait, random noise, etc.)

DZ (fraternal) twins are similar on a trait due to the genes they share (on average, 50%, same as any other full siblings) and the environment they share. They are different on a trait due to the genes they don't share (on average 50%), environment they don't share, and error.

These results say that the assumption that MZ twins share 100% of their genes is wrong. The real question is how wrong? Do MZ twins share 99.99% of their genes? Is that 0.01% difference right in the middle of some gene that has a large effect on the trait you're studying? For most of these new discoveries, it doesn't make any difference at all. Differences in silent mutations between twins isn't going to change scientists' conclusions that height is highly heritable (meaning: most of the difference in height between two people is due to the fact that they have different genes).

Re:Wonder how this affects... (3, Funny)

XavidX (1117783) | more than 6 years ago | (#22500520)

you mean eating your veggies does not make you grow big and strong?

Re:Wonder how this affects... (3, Informative)

mrami (664567) | more than 6 years ago | (#22501010)

I'll tell you what I first thought when I read this:

I read in, I think it was a Steven Pinker book, about studies done on identical twins using the big five personality traits [wikipedia.org] . What he said was that on the big five, identical twins raised together were roughly 50% similar, and identical twins raised apart were... roughly 50% similar. So when it comes to nature/nurture on the big five, you get 50% genetics, maybe 1-2% environment, the rest comes from ?????.

As you say, those numbers are probably based on the assumption of the genetic code being exactly the same, so those numbers can't represent reality as we know it now. But I'll be interested to see how the numbers fall out after the variance in twins' sequences is factored in. I would guess that it's the explanation for some of the ????? above, but how much?

Re:Wonder how this affects... (2, Funny)

zappepcs (820751) | more than 6 years ago | (#22501086)

The rest comes from the fact that you'd want to fucking be different too if they called you a "discordant monozygotic twin"

Re:Wonder how this affects... (1)

Oswald (235719) | more than 6 years ago | (#22500492)

Thank you for anonymously bringing this out, as it was the first thing I thought of when I read TFA. I guess if we hadn't already figured out that those experiments were fucked by shared prenatal nutrition (minor oversight, that), we could now stop loudly announcing that intelligence is 80% heritable.

Re:Wonder how this affects... (4, Insightful)

Eivind (15695) | more than 6 years ago | (#22500674)

Actually, scientists aren't (universally) that dumb.

If identical twins are much MORE similar in intelligence compared to non-identical twins, we can conclude that there is a high likelihood that the difference is genetic.

Identical twins should not normally have more similar nutrition (in pregnancy or thereafter) than nonidentical ones.

Re:Wonder how this affects... (2, Funny)

somersault (912633) | more than 6 years ago | (#22500898)

Actually, scientists aren't (universally) that dumb.
No, a scientist is smart. Scientists are dumb, panicky, dangerous animals and you know it.

Re:Wonder how this affects... (1)

joaommp (685612) | more than 6 years ago | (#22500884)

my twin brothers are actually quite similar... when one decides to annoy me, the other one gets automatically in the same mood...

Re:Wonder how this affects... (5, Interesting)

skjolber (933754) | more than 6 years ago | (#22501148)

As an identical twin myself, I have been included in several national studies. These studies typically address the differences between identical and non-identical twins. It was actually determined through conventional means that it was > 99% certain that we were identical twins, even after living apart for several years. I.e. you would not need DNA testing for determining who's identical i most if not all cases.

I really do not think this new information will affect previous studies much, because the loss in precition is probably much higher due to non-genetical, i.e. external, factors. However this new insight opens the door for new identical-only studies, where external factors also are kept to a bare minimum.

I would also like to point out that to a twin, it is clear that identical twins are in fact not equal. I my case we looked very alike untill about 20 years, however now (at 29 years) it is clear to everyone to see that there are clear (visual) differences. This should, in terms, tell all you non-twins that your current physical apperance (++) is actually one within a possible range you could have become, for better or worse.

--

Two for the price of one

News Flash! (3, Funny)

Strange Ranger (454494) | more than 6 years ago | (#22500050)

After the sperm penetrates the ovum [wikipedia.org] , a zygote [wikipedia.org] is formed. After which, chaos [wikipedia.org] ensues.

Growth and development of one copy != growth and development of the other.

Re:News Flash! (5, Interesting)

repapetilto (1219852) | more than 6 years ago | (#22500156)

Right, and it seems like their making a false dichotomy between environmental factors and DNA replication "errors," one can lead to the other (well replication errors can lead to susceptibility). Think about your skin cells, people who spend alot of time outside end up with their skin adapted. Its not just upregulation of whatever leads to more pigment, there is actually competition going on amongst the cell lines, those that survive better start to spread. Eventually even the whitest person you know will have permanently darker skin (if it doesn't kill them first that is). Same with every organ I imagine.

Re:News Flash! (1)

RiotingPacifist (1228016) | more than 6 years ago | (#22500160)

well its not chaos, but it is pretty obvious that changes are going to occur as soon as cells divide, especially when stuff goes wrong.

Re:News Flash! (5, Funny)

Anonymous Coward | more than 6 years ago | (#22500392)

well its not chaos...

You clearly do not have a four-year-old. Now if you'll excuse me, I've got to go vacuum the bookshelf. Don't ask.

Re:News Flash! (1)

Daimanta (1140543) | more than 6 years ago | (#22500978)

After the sperm penetrates the ovum, a zygote is formed. After which, chaos ensues.
Try telling THAT, to your children.

Disease gene hunting (3, Insightful)

reprint (1162711) | more than 6 years ago | (#22500072)

This is certainly another tool for those hunting genes associated with disease. These are complex diseases however with multiple genetic alterations so the identification of a single gene may not provide the whole story. Also a gene identified this way may not apply to the larger afflicted populaton since this is a correlation seen in a small study group. It should be relatively easy to check though.

Re:Disease gene hunting (1)

omfglearntoplay (1163771) | more than 6 years ago | (#22502340)

I semi-recently saw a TV program about "meta-geneticis" that claimed to answer the question as to why identical twins had differences and some got diseases, as well as several things relating to which genes are expressed or repressed. Supposedly meta-genetics (spelled?) is about which genes get switched on or off... and how environment affects that. The big example was an experiment with mice... one set of mice had a "mean" mom that didn't lick them (not enough nurturing), and they (if I recall) got really fat and their coat turned a weird color. The other set of mice had a mom that licked the tar out of them, and they repressed their bad gene that made them fat blondes. The fat ones then grew up to lick their children less, etc. They made the point that it was much much harder to understand/map meta-genetics than just genetics as it required most of the genetic code for a particular species to be understood before we could find the genes that were responsible for meta-genetics. My problem is I can't find anything on wikipedia or via a google search on this "science". Am I spelling it correctly, or is it a fake science or what? Any help on this is much appreciated. It is obviously *not* related to metagenesis: http://www.answers.com/metagenesis?cat=technology [answers.com]

Re:Disease gene hunting (2, Informative)

reprint (1162711) | more than 6 years ago | (#22502590)

If you search for meta-genetics (with the hyphen) you will find a pseudo-science which really has no mainstream scientific support. How genes connect with how an organism looks, behaves etc (phenotype) is quite complicated. Gene expression is controlled by many factors and new ones are being discovered. The term I think you are looking for is epigenetic or gene imprinting. I won't get into a long explanation because you can find good information by searching. If you look up gene expression, you will also find many method of gene expression control such as siRNA or the recent discovery of miRNA, a very hot area right now.

Go figure! (1)

gowakuwa (1199733) | more than 6 years ago | (#22500132)

They are like DEs in Linux. They are made of equally bloated code, and their functionality is exactly the same, but they will never be 100% compatible.

Twins aren't Identical? (4, Funny)

Anonymous Coward | more than 6 years ago | (#22500164)

Well, duh. [wikipedia.org]

Amazing breakthough! (5, Funny)

brit74 (831798) | more than 6 years ago | (#22500182)

I'm sure this will explain why the evil twin is evil. It's an amazing breakthrough in the field of soap opera science!

I cannot believe it (1)

antifoidulus (807088) | more than 6 years ago | (#22500186)

the article didn't even mention the Olsen twins!

Re:I cannot believe it (1)

somersault (912633) | more than 6 years ago | (#22500928)

I propose that it is our scientific duty to get them naked and carefully examine every inch of them to make sure that they are in fact "not identical after all".

Re:I cannot believe it (0)

Anonymous Coward | more than 6 years ago | (#22501162)

the article didn't even mention the Olsen twins!
Most of their adult fanbase lost interest in them when they reached the age of consent.

Don't deny it, you sick fucks!

Re:I cannot believe it (2, Informative)

geminidomino (614729) | more than 6 years ago | (#22501560)

No, most of their adult fanbase lost interest in them when Full House was canceled. Only the "sick fucks" and loser tweens have cared about them since.

Re:I cannot believe it (2, Insightful)

0100010001010011 (652467) | more than 6 years ago | (#22502254)

No most of their adult fanbase lost interest when they got scrawny and anorexic. The same with numerous other (what I would consider attractive) young female stars. Olsen Twins, Lohan, Spears, I'm sure Duff and Cyrus will follow suit. They were all decently attractive women until around 18 then they decided that being 95 lbs was more attractive than 130 (I'm sure drugs had nothing to do with it either). Other than Spears, she just went batshit crazy and needs some good drugs.

(Note, 18 is only the age of consent in the USA, they would have been perfectly legal earlier in other countries)

Dear women of slashdot (ha) quit trying to be a size -1.

Err..... (1)

Caedes.Leighton (1186201) | more than 6 years ago | (#22500212)

Whenever I read scientific articles like this I think "I could have sworn scientists already knew this..." I'm probably wrong but scientists seem to just be researching two things, new ways to kill or blindingly obvious.

Re:Err..... (2, Interesting)

repapetilto (1219852) | more than 6 years ago | (#22500244)

well you still have to research the obvious, because sometimes intuition is wrong. Ever hear the thing about how many times you would have to fold a normal piece of paper in half in order for it to reach the moon? Really guess. The answer is 42. And I'm not just saying that because its the answer to everything.

Re:Err..... (1)

mrbluze (1034940) | more than 6 years ago | (#22500384)

well you still have to research the obvious, because sometimes intuition is wrong.
And you still have to research new ways of killing people, because sometimes the ethics committees catch on to what you're currently up to.

Re:Err..... (3, Informative)

dltaylor (7510) | more than 6 years ago | (#22500312)

Blindingly obvious? It requires a tremendous ability to detect genetic differences when the difference is a nothing more than the number of copies of a few base pairs in an entire genome (~3,000,000,000 base pairs). We still don't know whether there are any epigenetic differences, or what those might be, because that is even more difficult to measure.

While it may seem obvious to the uneducated that twins are "different", there is a lot of research that shows high correlation, even when the twins are raised apart, so identifying the cause(s) of the differences and whether those are "nature" or "nurture" is still of value. Even within a family, the differences may be simply something like feeding order, where the earlier fed may get different (not necessarily better or worse) nutrition or bonding experience than the later fed, rather than, necessarily, a genetic difference.

When it is copy numbers, or very small polymorphisms, and there is some somatic variation, we can use the data to more closely identify which genetic values are associated with the variation.

Re:Err..... (1)

English French Man (1220122) | more than 6 years ago | (#22500404)

I heard about 4 studied cases of homozygotic twins which had different genders (a boy and a girl).

So, yes, in a way, it could seem "Blindingly obvious".

Mothers (1)

Merls the Sneaky (1031058) | more than 6 years ago | (#22500260)

Could this be why mothers can tell apart their twin offspring?

Re:Mothers (3, Funny)

ToxikFetus (925966) | more than 6 years ago | (#22502776)

Could this be why mothers can tell apart their twin offspring?
I find that a few well-placed scars do the trick.

Now excuse me while I meet with Child Services.

That was known for quite a while (5, Informative)

bogd (912084) | more than 6 years ago | (#22500362)

I remember that during medical school (maybe 7 or 8 years ago) we were told that while identical twins have extremely similar DNA to each other, that DNA is not 100% identical. Maybe 98 or 99% (more than any other two individuals on this planet), but not 100%. So while this is an interesting research, it hardly qualifies as "news"...

Re:That was known for quite a while (1)

Ihlosi (895663) | more than 6 years ago | (#22500402)

I remember that during medical school (maybe 7 or 8 years ago) we were told that while identical twins have extremely similar DNA to each other, that DNA is not 100% identical.

Well, quite probably not even all the cells of your body have 100% identical DNA.

Re:That was known for quite a while (3, Informative)

Rhabarber (1020311) | more than 6 years ago | (#22500526)

Hmm, you mean just like my DNA is 99% identical [psu.edu] to that of every chimp ;)

Also remember that many of your cells carry DNA of all those viruses you got exposed to without even noticing. And while we talk about infections, the immune system comes in mind, with all those crazy DNA recombinations taking place during its development. Not to mention spontaneous mutations which are not that insignificant tumorigenesis [wikipedia.org] .

Nobody actually ever believed that twins are 100% identical. They just want to make up their story. Nothing new to see here ...

Re:That was known for quite a while (1)

bogd (912084) | more than 6 years ago | (#22500582)

Hmm, you mean just like my DNA is 99% identical to that of every chimp ;)

I was wondering when this will pop up :) . It might be 99% for the chimp and 99.8% with the identical twin, or it might be 95% for the chimp and 99% for the twin. Somehow, I have a feeling nobody can give an absolutely accurate figure.

Re:That was known for quite a while (4, Funny)

Spacezilla (972723) | more than 6 years ago | (#22500944)

My identical twin IS a chimp, you insensitive clod!

Re:That was known for quite a while (1)

bogd (912084) | more than 6 years ago | (#22500998)

Oh yes, I thought I saw some resemblance there! :P

Re:That was known for quite a while (2, Funny)

Spacezilla (972723) | more than 6 years ago | (#22501302)

No, I mean... Ah, damnit, I walked right into that one, didn't I? :(

Re:That was known for quite a while (1)

geminidomino (614729) | more than 6 years ago | (#22501604)

AND got modded +1 informative for it, no less. The Mods are in rare form today.

Re:That was known for quite a while (0)

Anonymous Coward | more than 6 years ago | (#22501054)

I remember that during medical school (maybe 7 or 8 years ago) we were told that while identical twins have extremely similar DNA to each other, that DNA is not 100% identical. Maybe 98 or 99% (more than any other two individuals on this planet), but not 100%. So while this is an interesting research, it hardly qualifies as "news"...


In other news, humans and chimpanzees share 98% similar DNA. I'll leave the implications as an exercise to the reader.

chimps (1)

ecbpro (919207) | more than 6 years ago | (#22502584)

Well 98% similarity would be really low, this is actually the genetic distance between humans and chimps!
If you were right then ones twin brother could be a chimp :-)

Makes you wonder, doesn't it? (1)

hyades1 (1149581) | more than 6 years ago | (#22500416)

Maybe some of those small differences are reflected, for example, in whether one twin makes more efficient use of a particular protein than the other which in turn leads to tiny differences in how they make out on an identical diet, or with exposure to the same environment.

I wonder if this might in turn be reflected in small physiological differences that explain why people who know twins well can usually tell them apart when they're together.

what about... (0)

Anonymous Coward | more than 6 years ago | (#22500444)

identical cousins?

Copying introduces errors (3, Insightful)

tsa (15680) | more than 6 years ago | (#22500596)

When 3 billion basepairs are copied when a cell is divided, it seems logical to me that errors occur. So why isn't the fact that 'identical' twins are not truly identical a no-brainer to the experts? I know this remark sounds like a troll, but I'm genuinely surprised.

Re:Copying introduces errors (1)

ultrafunkula (547970) | more than 6 years ago | (#22500708)

I agree that it sounds obvious. But unless you prove it with research and experimentation then it's just a theory. Now that it can be proven we can use the fact to investigate how the differences in DNA impact genetic diseases, etc.

Re:Copying introduces errors (1, Informative)

Anonymous Coward | more than 6 years ago | (#22501468)

But unless you prove it with research and experimentation then it's just a theory^H^H^H^H^H^Hhypothesis.

Thanks.

Re:Copying introduces errors (3, Insightful)

mrbluze (1034940) | more than 6 years ago | (#22500720)

Scientific research is only as good as the people conducting it and what motivates them. From what I've seen, only a small number of people are genuinely excited by the stuff they are researching. The rest of them are chasing a PhD or some other claim to fame. But also coming up with a good study and designing it well to make it valid is not easy. It takes creative imagination and intelligence. Whilst there are many people with these qualities, it's frighteningly hard to find them at scientific meetings.

Re:Copying introduces errors (1)

croftj (2359) | more than 6 years ago | (#22500938)

It's because the obviousness of something is not obvious until it is scientifically proven to be obvious.

Re:Copying introduces errors (0)

Anonymous Coward | more than 6 years ago | (#22501132)

It wasn't the idea that was surprising. What is interesting and intriguing is the quantification of the amount of at least one type of variation that occurs.

Whenever you see a headline and think to yourself "wow, I knew that already. How come the experts didn't?", you should realise that the problem is almost certainly with the reporting of the story, and not with the experts.

Re:Copying introduces errors (1)

fireboy1919 (257783) | more than 6 years ago | (#22501926)

are not truly identical a no-brainer to the experts

Maybe it's because they know the rate of mutation for the human race (which seems like it should predict how likely errors that can cause disorders are to occur)?
Maybe because they know a lot about the mechanisms to keep errors from occurring?
Maybe this particular effect doesn't happen as much for non-twins?

This may explain WHY there are "identical" twins (3, Interesting)

mlwmohawk (801821) | more than 6 years ago | (#22500690)

I wonder, maybe the egg always splits when minor genetic errors happen as a method to protect the embryo. The vast majority of the time, the part that splits dies and is reabsorbed. On odd occasions, the genetic mutation is viable and becomes a twin.

That would imply that the second twin always has some sort of mutation from the first.

Re:This may explain WHY there are "identical" twin (1)

mrbluze (1034940) | more than 6 years ago | (#22500736)

Now there's a clever thought!

Re:This may explain WHY there are "identical" twin (1, Informative)

Anonymous Coward | more than 6 years ago | (#22501788)

I wonder, maybe the egg always splits when minor genetic errors happen as a method to protect the embryo.

Eh, from an evolutionary perspective there's another, simpler advantage to producing offspring at twice the rate...

Allergies (2, Interesting)

BenjiTheGreat98 (707903) | more than 6 years ago | (#22500920)

I've wondered about this. I'm going to get married to a twin in a couple months and my fiance is has many medical allergies - penicillin and similar drugs (like her mother). Her identical twin sister on the other hand has allergies such as pollen or other outdoor allergies.

I was never sure how much genes would play a role into this.

Re:Allergies (1)

slimjim8094 (941042) | more than 6 years ago | (#22501692)

slightly OT, but very small numbers of people are actually allergic to Penicillin. Around 20-30 years ago doctors thought that if you had some kind of reaction going on the medication, you were allergic to it. However, the kinds of illnesses treated with penicillin tend to 'put up a fight', as it were and cause a reaction as they are treated. Not to mention that most of these people had an adverse reaction ONCE, when they were 4 or something... Most 'allergic' people have no reaction to penicillin alone.

</random>

Re:Allergies (2, Interesting)

Peter Mork (951443) | more than 6 years ago | (#22502010)

(Caveat: IANAMB) As I understand it, immunoglobins are encoded by genes in so-called hypervariable regions. Basically, there are regions of the genome in which variability is beneficial because it allows the body to more easily generate immunities to various antigens. However, allergies turn the immune system against harmless antigens. So, if there's any genetic variation between identical twins, I would expect it to be in the hypervariable regions and therefore exhbited as differing allergies.

I Had Noticed Something (4, Interesting)

marzipanic (1147531) | more than 6 years ago | (#22500966)

As a proud mum of identical twin boys I had noticed that mine seem distant as opposed to those who feel empathy for each other.

They are part of a twin study, which basically involved some of the placenta, blood tests and for a few months DNA swabs from inside the cheek. The study never got back to us with the results yet as I believe it is still ongoing. But yes it was confirmed they are definitely identical.

As babies I used to "colour code" them so I knew who was who, now they are teenagers, totally different but I put it down to personality and obviously different tastes in dress. Silly me....

I will be following this with interest though! Esp. as one of my sons has autism and they are saying that could be a genetic thing, well I was told by a specialist if one had autism the other would have too? However my GP said that is crap. I have no idea but they are like chalk and cheese except for their voice.

Re:I Had Noticed Something (-1, Troll)

Anonymous Coward | more than 6 years ago | (#22501500)

Probably they just ate the placenta and told you it was for a study.

Your story reminds me of when I busted the seal on two twins back in 96. One of them was very tight whereas the other was not. Might have been due to similar genetic differences?

Re:I Had Noticed Something (0)

Anonymous Coward | more than 6 years ago | (#22501562)

I am distant to my twin sister and it's simply from experience, because moving to a small school and thereby always sitting next to your twin, being paried up with them, always being on the same team in sports and having idiots continually ask you "If one of you gets hurt does the other feel it." or "Can you read each other's minds." gets old in less than a year, even when you're younger.

The twin study won't get back to you.

The color coding thing, it happens, the worst thing about the same but different that inevitably happens was getting the same presents just slightly different in pattern or color. Really makes opening things less fun when you already know what it is.

Re:I Had Noticed Something (1)

tatonca (305375) | more than 6 years ago | (#22502538)

Very Interesting - Since you're here on Slashdot, I'm going to go ahead and assume you're as geeky as the rest of us... ;)

This article a while ago in Wired (http://www.wired.com/wired/archive/9.12/aspergers_pr.html) has some interesting details on how in the Silicon Valley area, the number of Autistic kids is higher than the national average, and how that may co relate to a particular mutation in the techie crowd...

I dismissed it as an interesting piece of circumstantial evidence until just the other day. I live in Canada, in RIM country - in recent years a great number of tech and science companies have brought their operations up here, including Google and McAfee to name very few. At any rate, my daughter told me she had an altercation with a specialist teacher who commented on her wardrobe ;) - when asked what she meant by specialist teacher, she told me she was from the Autism Program at her school. They had to separate the Special Programs into two to deal with the surge of Autistic kids in the region ...

A recent study by the CDC showed "that about 5.6 per 1,000 children aged 4-17 years had a parent-reported autism diagnosis." (http://www.medscape.com/viewarticle/531797)

There are 12 kids in the program, for a school population of 1500. (about a 42% increase over the average) There are similar programs in most of the schools in the region....

One could take this circumstancial evidence and form a hypothesis that, if they could isolate the differences in your two sons DNA, and then figure out the base pairs in you and your partner that this coding came from, they could be able to identify the conditions under which autism is more likely to occur...

What about mitochondial DNA? (1)

Mathinker (909784) | more than 6 years ago | (#22501040)

I may be missing something here, but it seems to me that the research only concerns nuclear DNA. I would guess that at least some (many?) pairs of "identical" twins have differences in their mitochondrial DNA, also.

mitochondrial, not mitochondial (1)

Mathinker (909784) | more than 6 years ago | (#22501062)

Sorry about the typo in the comment title...

Re:What about mitochondial DNA? (1)

sydbarrett74 (74307) | more than 6 years ago | (#22501170)

I'm speaking strictly as an amateur (and outsider) here, but I imagine the mechanism also exists for mtDNA. However because the mtDNA genome has ~16000 base pairs vs. the 3 billion base pairs of nuclear DNA, the difference would be proportionally that much greater. Any biologists willing to pipe up and tell me I'm on the right track or that I'm full of shit? :)

both of them say yes (1)

mjs_ud (849782) | more than 6 years ago | (#22501108)

They look so goddamn like the same person. They are twins, that is why. I would say to them "Do you want ice cream cone?" Both of them say yes!

or maybe (1)

Crock23A (1124275) | more than 6 years ago | (#22501276)

Or maybe these 'genetic' diseases aren't really genetic at all but caused by an environmental factor.

Re:or maybe (1)

Spy der Mann (805235) | more than 6 years ago | (#22501688)

Or maybe these 'genetic' diseases aren't really genetic at all but caused by an environmental factor.

Life itself was caused by an environmental factor. Go figure.

That's really not surprising (2, Interesting)

sexybomber (740588) | more than 6 years ago | (#22501732)

I can think of a scenario off the top of my head that'd be one plausible explanation for this sort of thing:

1. Egg gets fertilized
2. Egg splits into two fertilized eggs
3. Both eggs start dividing
4. After a few cell divisions, an extremely well-aimed cosmic ray strikes egg #2, shearing off a few base pairs from one of its copies of chromosome 3. Egg #1 is unaffected.

...

5. Egg #2 grows up to be the evil twin.

Cloning (1)

Glacial Wanderer (962045) | more than 6 years ago | (#22501792)

I wonder if this affects cloning in the same way? Maybe cloned food isn't really exactly the same...

i hate unstructured articles (1)

mapkinase (958129) | more than 6 years ago | (#22501864)

Do I have to go through all nine pages to find out what I want?

The American Journal of Human Genetics is a pathetic wallpaper for not enforcing the proper paper structure (Introduction, Methods, Results, Discussion). /rant

Obviously twins are not identical... (1)

volpone (551472) | more than 6 years ago | (#22502352)

...one of them must have a goatee. It's the law.

Yeah, DNA is identical, but... (5, Funny)

Mandovert (1140887) | more than 6 years ago | (#22502426)

...do MD5 match?

Epigenetics (3, Interesting)

ecbpro (919207) | more than 6 years ago | (#22502782)

Epigenetics is an important factor that should not be neglegted!
Depending on the life-style of each twin (and other factors) twins could be identical genetically but very different epigenetically. That means that even though they have the same set of genes they can be completely differently regulated, thus resulting in different susceptibility to diseases.
(For those interested: One important epigenetic mark is the methylation of DNA at Cytosines thus resulting in the shut-off of genes.)
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