THE sudden failure of a clever trick of inheritance may explain why certain cloning experiments fail, a new report suggests. It may also be behind the creation of some mammalian species.
A basic rule of heredity is that animals inherit two copies of every gene, one from each parent. In mammals, however, there is a strange twist to this rule known as imprinting. A small percentage of mammalian genes are biochemically marked or "imprinted" so that only the copy from one parent is switched on.
But Shirley Tilghman and her colleagues at Princeton University in New Jersey have found that this mechanism can go wrong. When they mated two closely related species of mouse,
Even more bizarrely, which imprinted genes were affected depended on which species contributed ...
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