Slashdot Mirror
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.
Operator, give me the number for 911!
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.
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!
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.
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.
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"...
http://xkcd.com/263/
;-)
The MAFIAA is a bunch of mindless jerks who will be the first up against the wall when the revolution comes
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.
-- Cheers!
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.
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
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.
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.
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.
...do MD5 match?
Now excuse me while I meet with Child Services.
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.)
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.
Clones are more different than identical twins. They start with th same DNA (just like a twin) but are subject to the same errors during development. In addition to that, however, they are growing in a different environment unlike twins who share at least the same environment for the first 9 months if talking about humans. Hence, clones are less similar than twins.
NSFW? (not safe for work?)
Okay well the Dalhmers may not be identical, but they are not the only twins featured in Playboy. I've seen differing breast sizes in other twins as well.
(Let's see - College Girls Special Edition, circa 1999, two hispanic twins. One has C size and the other has B size (approximately). I had figured one had eaten more fatty food, but maybe it's in the genes.)
The government is not your daddy. Its purpose is not to raid middle-class neighbors' wallets and give it to you.
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?"