Regulation is needed to govern rapidly expanding research in animals containing human tissue or genes, according to the Britain\'s Academy of Medical Sciences. Using animals with limited humanized traits is not new. Genetically engineered mice containing human DNA are already a mainstay of research into new drugs for diseases like cancer. For instance, Chinese scientists have already introduced human stem cells into goat fetuses and U.S. researchers have studied the idea of creating a mouse with human brain cells. But Martin Bobrow, a professor of medical genetics at the University of Cambridge, who led the Academy\'s working group, said there were three areas of particular concern. \"Where people begin to worry is when you get to the brain, to the germ cells, and to the sort of central features that help us recognize what is a person, like skin texture, facial shape and speech,\" he said. His report recommends that government should put in place a national expert body, working within the existing system for regulating animal research, to oversee such sensitive areas. British ministers said they welcomed the report and would consider its recommendations carefully.