TIMELINE: ANIMALS WE’VE CLONED
German biologist Hans Driesch takes a two-cell sea urchin from the Bay of Naples and shakes it in beaker of water. The cells part, giving rise to two, independent but identical, sea urchins.
Hans Spemann, another German scientist, uses a fine hair from his baby son to split a salamander embryo in two. The result: two amphibians for the price of one.
In the US, Robert Briggs and Thomas King perform a successful nuclear transfer, by moving a nucleus from an embryonic frog cell into an egg cell whose own nucleus had been removed.
Instead of using nuclei from frog embryos, Oxford biologist John Gurdon takes them from adults, demonstrating that a differentiated nucleus still has the power to build an entire animal.
Chinese embryologist Tong Dizhou applies the same technique to fish, though his work, originally published in his native Chinese, does not receive much attention beyond China.
The cloning of Dolly the sheep builds on Gurdon’s method, showing that the nucleus from a differentiated cell retains the ability to make an entire animal from scratch, even in mammals.
A team led by Prof Gerald Schatten create Tetra, a rhesus macaque, using embryo splitting. Here, the cells in the embryo are split after reaching the eight–cell stage to create four identical two-cell embryos.
Researchers at Texas A&M University create the first cloned pet, using a cell from a brown-and-white tabby cat called Rainbow to make
‘CC’ (aka ‘Copy Cat’ or ‘Carbon Copy’).
Scientists at Advanced Cell Technology in the US are the first to clone an endangered species.
Noah the gaur, a species of wild ox native to Asia, dies from dysentery after two days.
Korean scientist Hwang Woo-Suk uses the ear cell from an Afghan hound to make Snuppy, the world’s first cloned dog. A Labrador acts as surrogate mother.