[For Press & Publications] LEICESTER UNIVERSITY GENETICISTS PROVE AUTHENTICITY OF CLONED SHEEP



July 1998

No 104

STRICTLY EMBARGOED UNTIL 7PM WEDNESDAY JULY 22

LEICESTER UNIVERSITY GENETICISTS PROVE AUTHENTICITY OF CLONED SHEEP

DNA fingerprinting - the revolutionary technique invented by Professor Sir Alec Jeffreys at Leicester University - has been used in the world-renowned Department of Genetics to independently authenticate the origin of the sheep Dolly, the first mammal ever to be cloned.

Professor Sir Alec Jeffreys and his team at Leicester University today (July 23) confirmed their findings in an article published in the scientific journal Nature. Their results proved `beyond reasonable doubt that Dolly is indeed derived from a cell of the mammary tissue taken from the adult donor ewe', said Dr Esther Signer who carried out the analysis.

The Genetics team - Professor Jeffreys, Dr Signer and Dr Yuri Dubrova - were asked to perform DNA fingerprinting on samples from Dolly and the donor sheep, plus additional sheep as controls. This followed concerns about Dolly's origin - i.e. whether she could have been derived not from a mammary cell of the adult donor sheep, but from a contaminated sheep cell culture or from a fetal cell in the udder of the pregnant donor.

Dr Signer said: "Leicester University was approached at the start of the year to carry out the tests which we completed in May. Leicester was chosen because of its world reputation for pioneering excellence in this field. DNA fingerprinting is applied the world over mainly to identify individuals and to verify paternity in humans and in animals. It is a powerful alternative to microsatellite analysis, the method used originally by Dolly's creators to demonstrate her authenticity."

Explaining the technique used at Leicester University, Dr Signer said:

"We used two novel and independent sets of probes to produce suitable DNA profiles in sheep. We then compared Dolly's blood with udder tissue from the donor ewe and cells derived therefrom. Blood samples from unrelated sheep served as controls.

"We found that DNAs from Dolly, the udder and the cells were indistinguishable in terms of band number, position and relative intensity. We also found that each control sheep had a clearly different pattern. From the estimated probabilities that an unrelated sheep or an offspring would have, by chance, an identical DNA fingerprint as the donor ewe we conclude that it is extremely unlikely that Dolly could have been derived from a contaminated cell culture or from a fetal cell."

Dr Signer added: "Carrying out these tests to determine whether or not Dolly is a clone was very exciting although the procedure was not much different than those we regularly use for testing individuals, twin zygosity and parentage."

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