An international team of scientists led by Dr RyuzoYanagimachi from the University of Hawaii in Honolulu has cloned more than 50 mice in several experiments, using a new technique that represents a significant step forward in cloning technology (Nature 1998;394:369-74).

In the same issue of Nature, scientists at the Roslin Institute in Scotland have been cleared of accusations that Dolly, the first mammal to be cloned from differentiated adult cells, was not in fact a clone. Two groups of researchers have shown by microsatelliteanalysis and DNA fingerprinting that Dolly is a true clone (Nature 1998;394:329 and 329-30).

Dr Teruhiko Wakayama, a researcher at the University of Tokyo, pioneered the new cloning technique, which involved injecting nuclei from terminally differentiated somatic cells (Sertoli, neuronal, and cumulus cells) into enucleated mouse oocytes. The oocytes were left …