WHY IDENTICAL TWINS ARE DIFFERENT FROM EACH OTHER.

WHY IDENTICAL TWINS ARE DIFFERENT FROM EACH OTHER. Slate has had a special feature with good articles on twins, which, of course, are always interesting to me. Brian Palmer in this article points out the flaws in any scientific study that assumes that identical twins are genetically the same (“pretty much useless” says the headline). Monozygotic (identical) twins do not have identical DNA. “Copy number variations” make up about 30% of a person’s genetic code. In addition, there are mutations during development which affect about 10% of brain cells. Identical twins have different mitochondrial DNA. And the environment in the womb and afterward affects the way in which when genes are transcribed. Given all this, it is amazing that we identical twins look as much alike as we do.