Doubting Dolly

The first pure cloned mammal comes under a cloud

Published: Thursday 30 September 1999

The world's first cloned mammal, Dolly, may not technically be a clone, but a mix of two animals. It is therefore a chimera with two mothers, rather than a pure clone, says a recent report in the journal Nature Genetics. "Whereas the controversy over the origin of Dolly's nuclear DNA has been resolved -- she is derived from the DNA of an adult donor's mammary cell -- the source of her mitochondrial DNA -- the cell's other genetic material, remains unknown."

The mitochondria, the powerhouse of the cell, fuels cellular processes. The investigation on the origin of the mitochondrial DNA of Dolly, which was conducted by creators of Dolly, including Ian Wilmut at the Roslin Institute in Scotland and Eric Schon and his colleagues of Columbia University, have published their work in the September issue of Nature Genetics. Their research revealed that in all cases, the mitochondrial DNA from the cloned animals differed from that of the nuclear donor cells, but were similar to that of the recipient egg cells. This suggests that only the recipient egg cells contribute mitochondrial DNA to clone animals. If confirmed, this study will have implications for the potential use of this cloning method to correct inherited mitochondrial diseases.

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