COMBINING two or three cloned embryos to make a single one greatly increases the chances of a live animal being born.
Cloning has always been very inefficient, with hundreds of embryos having to be created to get a few live births. The cloned embryos of many species also have fewer cells than normal and often do not express genes that are key to development, such as Oct-4. So K. John McLaughlin at the University of Pennsylvania, in Philadelphia, wondered if adding more cells to cloned embryos might improve their chances.
His team created genetically identical cloned mouse embryos using cells…
