This week, mouse cloning expert Teruhiko Wakayama, along fellow colleagues at the Center for Developmental Biology at Japan's RIKEN research institute in Yokohama, managed to clone mice from dead bodies that had been frozen for sixteen years.

The team of scientists informed they had used the nuclear transfer technique in order to clone the mice, which entails replacing the nucleus of an egg cell with another nucleus from a somatic cell (any cell forming the body of an organism). After the replacement, the egg cell undergoes stimulation by shock so that it begins dividing and further develops an early stage embryo that has almost identical DNA to the original organism.

Wakayama and the other researchers were able to clone the mice despite the fact that their cells had been rendered to burst due to the freezing, which causes the DNA to degrade. The mainstay method to prevent this from happening is cryopreservation, a processes that preserves cells and tissue by cooling to  −196 °C, the boiling point of liquid nitrogen, but for it to work, cryoprotectants need to be used before freezing the organisms in question.

After having tried to clone the animals by using cells from various organs, the Japanese scientists discovered that the brain cells were the most likely to lead to the sought after result.

In the Proceedings of the National Academy of Sciences, the team wrote that their accomplishment raised hope for being able to preserve endangered species in the future, adding though that cloning a mammoth (given that mammoth bodies have been found frozen inside blocks of ice) was almost impossible, by virtue of irreparable damage to the DNA.