WASHINGTON Making human-animal embryos for scientific experiments should be allowed because of the benefits to science and medicine, British experts said in a report released for Sunday.
Such embryos should never, however, be implanted into either a woman or an animal, said the Academy of Medical Sciences.
The combinations would include animal eggs and the nucleus, containing the genetic material, of a human being, or human embryos that carry the genetic material of an animal, the independent advisory body said.
A cloning technique called somatic cell nuclear transfer, or SCNT for short, involves removing the nucleus from an egg cell and replacing it with the nucleus of a cell from the animal to be cloned -- perhaps a skin cell, for instance.
Scientists have tried this using, for example, an egg cell from a cow and a human nucleus.
There are no laws against it in either Britain or the United states and the independent Academy said it should remain legal.
"Provided good laboratory practice is rigorously followed, research involving cytoplasmic hybrids or other inter-species embryos offers no significant safety risks over and above regular cell culture research," said Martin Bobrow of Britain's Wellcome Trust, who chaired the panel making the recommendations.
"UK legislation permits research on human embryos under license from the HFEA (Human Fertilization and Embryology Authority) up to 14 days in the laboratory," Bobrow added in a statement.
"Re-implanting human embryos into a woman or animal is not permitted. There are no substantive ethical or moral reasons not to proceed with research on human embryos containing animal material under the same framework of regulatory control," he said.
Researchers want to make clones for a variety of reasons, but one of the most contentious is as a source of embryonic stem cells.
These powerful stem cells can give rise to any cell or tissue type in the human body and the hope is some day they may be used to tailor medical treatments for injuries or diseases such as Parkinson's or diabetes.
In some countries, such as Britain, their use is not controversial and is actively funded and encouraged. In the United States, their use is legal but federal funding of the work is strictly limited by Congress and by President George W. Bush, who has vetoed legislation that would broaden it.
Researchers also routinely make chimeras -- animals that contain the genetic material from more than one individual. These include animals that carry human genes, most commonly mice engineered with human genes that are used to study disease.
"We found no current scientific reasons to generate 'true' hybrid embryos by mixing human and animal gametes (eggs and sperm). However, given the speed of this field of research, the working group could not rule out the emergence of scientifically valid reasons in the future," Bobrow said.