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Identical Twins Not Identical After All
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.""
You think they are exactly the same, but they are always slighly different.
Knowledge is power. Knowledge shared is power lost.
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".
An Eye for an Eye will make the whole world blind - Gandhi
What gene difference made those twins so different (Danny de Vito and Arnold Schwarzenegger)
...decades of experiments that assumed twins have identical DNA. One twin may not be such a good control after all...
After the sperm penetrates the ovum, a zygote is formed. After which, chaos ensues.
Growth and development of one copy != growth and development of the other.
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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.
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.
Well, duh.
I'm sure this will explain why the evil twin is evil. It's an amazing breakthrough in the field of soap opera science!
the article didn't even mention the Olsen twins!
Monstar L
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.
Could this be why mothers can tell apart their twin offspring?
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"...
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.
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identical cousins?
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.
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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.
Now there's a clever thought!
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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.
:wq
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.
In the name of sticking up for someone with autism, f**k you! Prejudiced bastard.... that is unlawful and linuc for dumm
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.
Sorry about the typo in the comment title...
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!
return EXIT_SUCCESS;
Or maybe these 'genetic' diseases aren't really genetic at all but caused by an environmental factor.
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.
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...
I wonder if this affects cloning in the same way? Maybe cloned food isn't really exactly the same...
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Do I have to go through all nine pages to find out what I want?
/rant
The American Journal of Human Genetics is a pathetic wallpaper for not enforcing the proper paper structure (Introduction, Methods, Results, Discussion).
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...one of them must have a goatee. It's the law.
...do MD5 match?
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
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.)
and let my twin do the time. Does that mean they can tell us apart now?
Unfortunately the article does not seem to address the fact that there are other possible causes. Many environmental factors can affect DNA over time. For example, genes commonly have two attributes associated with them: penetrance and expression. Just because you have a gene doesn't mean it will necessarily be transcribed (i.e. does it get expressed?). Both internal and external cues can help determine this event occurring. Even when the gene does get expressed, how many copies get made can vary (penetrance).
These are the two of the most classic examples of differences between genes, but there are other mechanisms that exist. For retrograde viruses can insert themselves into genes.
Not to say their theory of CNV is wrong, just that other mechanisms have already been known.
http://www.redeldorado.com/images/svibe_2002/people8.jpg http://wizardofodds.com/photos/triplets_22k.jpg
Sisters, fraternal twins, ... but all from one egg? They're easy to tell apart, even when they try to look identical.
Advocates of strong genetic determinism (including defenders of the book "The Bell Curve") base most of their assumptions regarding behavioral and cognitive traits on twin studies, which assume that monozygotic twins are genetically identical. This pretty much upends such research and, thus, the strong deterministic position (there are generally more behavioral correlates than genetic correlates for traits such as IQ, anyway). There were actually other problematic assumptions, as well, such as 50% variance among siblings and 100% variance among non-related individuals, that undermined these studies before this, but it really seems to be the final nail in the coffin.
- Anonymous Robbie Clark
Are ALL of these twins showing minute genetic differences? From one sperm and one egg, should such a thing shouldn't be happening? It may be possible that these minute changes may have something to do with the original split of embryos in the fetus.
I won't even read the article. Slapstick on the mod's part. Epigenetic markers determine gene expression. In yourger twins, one will see a congruency in genotype. It is exposure to the environment that alters the genotype of one twin, effectively distinguishing that individual from its identical sibling. GOOGLE: EPIGENETICS NOVA for the layman.
Anyone who knows identical twins very well at all could have told you this.
I married one. From the day I met them, I have had no trouble telling them apart, even the one time her sister tried to fool me as a practical joke.
I suppose it's good to know the details; knowledge is generally good. But the announcement that identical twins aren't is right up there with "Politician caught lying!" My immediate thought is "Wow! Really! Who knew?"
I was an only twin for some time and observed that I was more identical than my sibling, who had a curious tendency to lurk in dark places cursing under his breath. He had appalling dental hygiene and was slightly taller despite his stoop. Eventually I traded him in on a second hand Volkswagen.
Now wash your hands.
Incorrect. The proper way twins in nature are produced is by two separate eggs. Also, because babies born as twins are much more likely to be stillborn or disabled, we can assume these sorts of pregnancies are evolutionarily accidental.
I'm a twin, so do I just hope that my brother develops all the disease and I stay healthy?
Researchers discover human `diff` _is_ useful... isn't this the natural title for /.?
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 recently heard a lecture on the genetics of autism - to summarize, there's only a 90% influence of genetics - there's still a 10% unaccounted-for 'trigger' (or something not understood). These results were based on twin studies. Basically, your non-autistic boy only had a 10% chance of not being autistic, but there it is - he's one in ten.
Of note, he does have the genetic pre-disposition, so some care should be made in his choice of a wife.
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