However, the technique is so close to the "cloning" technology used to create Dolly the sheep that it will raise difficult ethical questions for doctors.

BBC: Gene technology

Many doctors, including some at the forefront of cloning technology, have expressed severe doubts about whether the techniques could ever ethically be used on humans.

BBC: 'Ban IVF for smokers and drinkers'

But scientists are keen to develop the cloning aspects of the technology because this would yield perfect match tissue that would not be rejected by the patient.

BBC: UK to 'approve therapeutic cloning'

The citation for his knighthood credits Prof Wilmut with "revolutionising" biology through the cloning technique which underpins the science of stem cell technology.

BBC: Dolly the sheep creator knighted

The best-known of the new knights is Professor Wilmut, who is said to have revolutionised biology by successfully pioneering the cloning technique that underpins the science of stem cell technology.

BBC: Dolly creator heads Scots honours

With human cloning technology just around the corner and enough frozen sperm in the world to already populate many generations, perhaps we should perform a cost-benefit analysis.

WSJ: Best of the Web Today

In his State of the Union address, President George W. Bush advocated outlawing all use of cloning technology on human cells.

FORBES: Magazine Article

Less successful was the cloning of the gaur, a species of ox found in south Asia, by researchers at Advanced Cell Technology, a biotech company in Worcester, Massachusetts: the clone died of infection days after birth.

ECONOMIST: Endangered species