Unsafe cloning
scientists have found an evidence to show that even seemingly normal-looking clones may harbor serious abnormalities affecting gene expression that may not manifest themselves as outward characteristics. The findings, reported by researchers at the Whitehead Institute for Biomedical Research and University of Hawaii, confirm the previous suspicion that reproductive cloning is not only inefficient, but also unsafe ( Science , July 6, 2001).
In the study, scientists from Rudolf Jaenisch's laboratory and Ryuzo Yanagimachi's laboratory sought to examine the mechanisms underlying poor survival and gross overgrowth in cloned animals. They made mouse clones from embryonic stem ( es ) cells and monitored the activity of imprinted genes