Cloned mice follow Dolly

Cloned: 50 genetically identical mice

First there was Dolly the cloned sheep. Now there is Cumulina the cloned mouse and 50 others. Our science editor Dr David Whitehouse reports.

It is the most important step in genetic engineering since the 1996 birth of Dolly, the first mammal cloned from an adult.

An international team of scientists have produced 50 cloned mice using a similar technique to the one that produced Dolly.

To do it they took so-called cumulus cells that normally surround the ovaries of female mice and extracted the genetic material from them.

This was then transplanted into another mouse cell from which the original genetic material had been removed.

The cell was then transplanted into a pregnant female mouse.

The first cloned mouse, named Cumulina, was born on 3 October 1997. But its birth was kept secret.

Scientists have made three generations of clones and now have 50 mice that are all genetically identical.

Three generations of clones have been produced

The technique is a little more straightforward than the one that produced Dolly. It might be easier to apply to cattle, pigs and other animals.

Only 2% of the cloned embryos developed into healthy mice. Scientists regard this as a relatively high success rate for such a new technique.

Ian Wilmut of the Roslin Institute where Dolly was born said: "These are exciting results. They suggest that it will be possible to produce adult clones from a range of different cell types and species."

Davor Solten of the Max Plank Institute in Germany said: "Its importance cannot be overemphasised."

Cloning research could have many medical and scientific applications including producing pigs that have been genetically engineered to have human-compatable hearts.

Genetically modified cows with human compatible blood could also be mass produced. It could also be used to preserve lines of livestock as well as saving endangered species.

This research could also restart the debate about the possibility of cloning humans.

It demonstrates that technically a human could be cloned even though it would be illegal in most countries.

Few reputable scientists would consider performing such an experiment at this time.

The new research is described in the scientific journal Nature.