Mind & Brain Jumping Genes in the Brain Ensure That Even Identical Twins Are Different How can identical twins grow up with different personalities? "Jumping genes" move around in neurons and alter the way they work By Fred H. Gage and Alysson R. Muotri THIS IS A PREVIEW. Buy this digital issue or subscribe to access the full article. Already a subscriber or purchased this issue? Sign In Jean-Francois Podevin Your brain is special. So is mine. Differences arise at every level of the organ’s astonishingly intricate architecture; the human brain contains 100 billion neurons, which come in thousands of types and collectively form an estimate of more than 100 trillion interconnections. These differences, in turn, lead to variances in the ways we think, learn and behave and in our propensity for mental illness. THIS IS A PREVIEW. Buy this digital issue or subscribe to access the full article. Already a subscriber or purchased this issue? Sign In Buy Digital Issue $7.99 Add To Cart Digital Issue + Subscription $39.99 Subscribe ADVERTISEMENT Scientific American is a trademark of Scientific American, Inc., used with permission © 2015 Scientific American, a Division of Nature America, Inc. All Rights Reserved.