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Summary
In theory, the behavior of inbred mice reared and housed under seemingly identical conditions should be as similar as their perfectly matched genes. But, to the frustration of researchers, the rodents don't act like exact copies of each other. Of the possible explanations for such differences, researchers have found evidence for a particularly unexpected one: jumping genes in the brain. Formally known as transposable elements, they are small bits of genetic material that can move around the genome. They have generally been seen as troublemakers; when they jump, they can land in places that cause mutations or otherwise skew the expression of important genes. But some researchers argue that such changes might have a positive side, helping to generate diversity in brain cells. Such diversity might be important in brain development, they think, providing the raw material for building a flexible organ able to react to new environments and situations. And because a transposable element creates a slightly different genome each time it moves, it could explain why genetically "identical" mice aren't identical after all. It's far from a proven idea, but it has started to gain attention among geneticists who study jumping genes.
