Cloning trouble down to missing C?

9 February 2001

Cloning trouble down to missing C?

MISSING carbon atoms on genes might be responsible for the problems often associated with cloning animals.

Researchers at Edinburghs Roslin Institute believe that missing methyl groups attached to genes are the reason why some cloned animals are often born sickly or unusually large and many do not live for long. This change alters how actively genes produce proteins which are key to the animals survival, says a report in New Scientist (Feb 2).

The discovery may allow researchers to screen embryos produced by cloning and other test-tube techniques. This would allow faulty embryos to be eliminated before they are implanted into a surrogate mother.

The missing methyl groups discovery was made through studying sheep produced via AI which suffered from large offspring syndrome. Researchers found these sheep often lacked all the methyl groups on a gene for one particular protein which stops the foetus from growing too large, and produced 30-60% less protein than normal.

Roslin researcher Lorraine Young believes that clones may suffer from a greater number of defects than large offspring animals because the embryos undergo greater manipulation and may, therefore, lose more methyl groups from more genes.

Problems with cloned animals are well known – Roslin researchers produced 277 cloned sheep embryos before achieving a live birth with Dolly. &#42

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