Identical twins aren't

http://www.physorg.com/news122300048.html

" "Even though the genome is virtually identical in identical twins, our
results show that there in fact are tiny differences and that they are
relatively common. This could have a major impact on our understanding of
genetically determined disorders," says Jan Dumanksi, who co-directed the
international study with his colleague Carl Bruder. "

"These researchers studied 19 pairs of identical twins and found that they
indeed had the same DNA but nevertheless evinced differences in the number
of copies of individual DNA segments. A segment might be missing, or more
copies might exist in one twin. This could explain how one identical twin
can be afflicted with a disorder while the other twin remains fully healthy,
according to the scientists. "


No word on how to tell which one is "the evil twin".