Attack on the Clones: The High Fatality in Cow Cloning Explained

The 20th anniversary of cloning Dolly the sheep has marked two decades of scientific advancement but many cloned embryos still fail to make it to term. Researchers from the U.S. and France studied gene expression in developing clones and they've discovered that majority of losses are due to embryonic death, a failure during the implantation process, or the development of a defective placenta.