Studies of twins, particularly identical twins, have taught much about genetic individuality.  Identical twins have the same DNA, but develop in separate amniotic sacs with different umbilical cords.  In their isolated environments, then, DNA modifications occur—e.g. methylation that alters gene expression of a single gene and in total, entire genomes. Consequently, each individual, including conjoined identical twins, has a unique epigenetic profile, according to researchers at the Murdock Children’s Research Institute in Parkville, Victoria, Australia.  MORE