i always thought twins were one egg and two sperm... that alone should be able to account for the difference. or is that fraternal twins?
Posted on 03/15/2008 12:24:17 AM PDT by neverdem
Really?
THE FACTS
It is a basic tenet of human biology, taught in grade schools everywhere: Identical twins come from the same fertilized egg and, thus, share identical genetic profiles.
But according to new research, though identical twins share very similar genes, identical they are not. The discovery opens a new understanding of why two people who hail from the same embryo can differ in phenotype, as biologists refer to a person’s physical manifestation.
The new findings appear in the March issue of The American Journal of Human Genetics, in a study conducted by scientists at the University of Alabama at Birmingham and universities in Sweden and the Netherlands. The scientists examined the genes of 10 pairs of monozygotic, or identical, twins, including 9 pairs in which one twin showed signs of dementia or Parkinson’s disease and the other did not.
It has long been known that identical twins develop differences that result from environment. And in recent years, it has also been shown that some of their differences can spring from unique changes in what are known as epigenetic factors, the chemical markers that attach to genes and affect how they are expressed — in some cases by slowing or shutting the genes off, and in others by increasing their output.
These epigenetic changes — which accumulate over a lifetime and can arise from things like diet and tobacco smoke — have been implicated in the development of cancer and behavioral traits like fearfulness and confidence, among other things. Epigenetic markers vary widely from one person to another, but identical twins were still considered genetically identical because epigenetics influence only the expression of a gene and not the underlying sequence of the gene itself.
“When we started this study, people were expecting that only epigenetics would differ greatly between...,”
(Excerpt) Read more at nytimes.com ...
Sending to my identical twins...don’t ever try to play a game of chance against them. ;)
Not surprised: twins have different fingerprints.
Epigenetics is going to be the next great field in medicine.
What the article says is the they DO have identical DNA, but that changes can develop soon after fertilization. Another case of the headline being written by an brain-deficient moron.
What happens, is every time the cells divide, there are changes occurring. In other words, the succeeding generation of cells is not quite identical to the original cell. It can certainly make for some interesting differences in characteristics of a set of monozygotic twins, while there are still a lot of similarities.
Twin ping.
Great information, neverdem. Thanks for posting this!!
There is only a suggestion that this isn't the case (which is the case for some, and if all the cells in a twin are taken into account, not only the first one).
i always thought twins were one egg and two sperm... that alone should be able to account for the difference. or is that fraternal twins?
So their DNA is the same.....but different.
ping
thx... my Mom's twin was her Brother. 8^)
“Monozygotic twin” sounds pretty cool...maybe that will replace the expression “identical twin.” Discordant monozygotic twins would be identical twins who fight a lot with each other.
Good point. And they sure do change into different beings as they grow older and things happen to them.
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