Plans by doctors to clone the first human being were blasted Tuesday by one of the world's top experts in animal cloning, who warned of a high risk that the child may die prematurely or endure life as a cripple.

"People who suggest that they can copy humans basically have no real understanding of all the processes that can occur in an embryo to make cloning work," Lorraine Young, a researcher at Roslin Institute in Edinburgh, told reporters.

"In cloning, there's quite likely lots of things can go wrong... it's extremely complicated and we can't pretend to begin to understand it."

In addition to moral objections, there was a fundamental risk of safety, she said. Early death or ill health to the cloned child are "another reason why we just shouldn't do it," Young said firmly.

The Roslin Institute is one of the world's top authorities on cloning, creating the world's first artificially replicated mammal -- Dolly, a Finn Dorset sheep born on July 5 1996.

Young said that research on cattle and sheep found that up to 95 percent of cloned embryos died during pregnancy and of those who survived, some died soon after birth while others survived, but with serious abnormalities.

"There can be a wide range of problems," she said. "There can be considerable problems with the heart, or the lungs don't function very well. Often the animals are born OK but they can't breathe properly, so a lot of them die soon after their birth.

"However, there are definitely some cloned animals which are born and seem completely normal and can reproduce, for example Dolly has had several lambs and is a few years old, whereas other cloned animals make it to birth and die straight away, some make it to a week of birth and then die."

"We don't really understand why it happens. It's very odd. When you culture or clone embryos in cattle and sheep, you can get a whole range of abnormalities."

Young said it was difficult to calibrate the potential safety risk in cloning people, but said she "wouldn't be surprised if similar things also did happen in humans."

A private consortium of international doctors says it wants to clone a human being within the next two years. The declared goal is therapeutic, to help infertile couples have their own biological child.

Among those who have put their names to the project are Panos Zavos, a University of Kentucky professor of reproductive physiology, and Italian physician Severino Antinori, who has been in the headlines for trying to help post-menopausal women become pregnant.

The idea of human cloning has been condemned by moral, scientific and religious authorities and many countries have passed strict legislation to outlaw it.

A clone is an identical reproduction of its mother or father, depending on the genetic donor. The only clones that occur in nature are identical twins.

Animal cloning entails extracting the nucleus from a donor's cell and injecting into a fertilised egg whose own genetic material has been removed.

The fused cells then begin to grow and divide like a normal fertilised egg, to form an embryo, with the DNA from the transplanted nucleus providing the genetic "instructions" that will determine the offspring's physical characteristics.

Young suggested the reason for the problems with clones lay in the fundamental fact that adult cells -- while theoretically creating an exact clone of the original body -- have somewhat limited functions and cannot perform like embryo cells, which have to carry out myriad tasks.

"When you take an adult cell and you try against nature, if you like, to make it into an embryo cell, there are so many processes in that cell that have to be changed that there could be lots of things going wrong."

(From ChinaDaily)