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Tuesday, 25 January, 2000, 10:06 GMT
Japanese make clone of clone

Calf The animal was born on Sunday night

Japanese researchers say they have produced a cloned calf using a cell taken from an animal that was itself a clone.

It is the first case of a clone being produced from another clone of a large-sized mammal. Scientists have previously made copies of cloned mice.

The bull calf was born on Sunday night at the Kagoshima Prefectural Cattle Breeding Development Institute, Osumi, in the south of the country.

The work is part of a project to study life expectancy and ageing in cloned animals by comparing the cells and chromosomes of clones from different generations, a spokesman said.

"There is speculation that cloned animals may not be as healthy or live as long as normal animals,'' said Norio Tabara, one of the research scientists involved in the project.

Short telomeres

Longevity has now become a central issue for scientists as they master the new technology of cloning. Dolly the sheep, the first mammal to be cloned from an adult cell, is known to have unusually short telomeres.

Telo Telomeres cap the ends of chromosomes
These nubs of protein and nucleic acid protect the ends of chromosomes, the large structures that bundle up all the nuclear DNA in a cell. Short telomeres may indicate a shorter lifespan for a cell, which may mean cloned animals die earlier than normal animals.

Debate has raged as to whether four-year-old Dolly, cloned from a six-year-old sheep, is really ten.

This issue may not be a big problem in cloned livestock that have been made to produce better meat or make drugs, but it does have serious implications for the use of cloned tissue in human transplants. Doctors would be concerned about the length of time cloned cells might survive once inside the body.

Surrogate mother

The new bull calf was cloned from tissue taken from the ear of a calf last April when that animal was itself only four months old. The first animal was cloned from a 16-year-old bull.

The genetic material was fused with an unfertilised egg that had been stripped of its nucleus and placed in the womb of a surrogate cow. The resulting bull calf weighed nearly 44.8 kg (96.8 lbs) at birth.

The primary purpose of the Kagoshima institute's project is to produce tasty beef.

"Our objective is to produce good cattle consistently,'' said Norio Tabara. "If there is a stud that's of the highest quality, we want that bull to be available more widely.''

Head of the institute, Takaharu Yoshiya, said: "I think, with this recloning technology, we will be able to repeatedly use the cattle of good quality and of high ability."

Cloning also reduces the amount of time needed for reproduction. The tissues of an animal as young as three months can be used for cloning, while cows do not mate naturally until they are about 14 months old.

Another second-generation clone is due in late March, the researchers said.

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See also:
06 Jan 00 |  Sci/Tech
Old cells give new clones
03 Sep 99 |  Sci/Tech
Cloning gives second chance for bull
05 May 99 |  Sci/Tech
Cloning may damage long-term health
27 May 99 |  Sci/Tech
Is Dolly old before her time?

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