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A sheep cloning how-to, more or less


February 24, 1997
Web posted at: 8:50 p.m. EST

From Correspondent Ann Kellan

ATLANTA (CNN) -- However difficult the ethical questions, the procedure used to clone Dolly the lamb is not very complicated, according to scientists.

movie icon (512K/28 sec. QuickTime movie) - Slide show explanation on how cloning works.

In fact, scientists at Scotland's Roslin Institute and other laboratories have previously cloned animals from embryos. What makes Dolly unique is that she was cloned from a single cell of an adult animal.

Most experts thought that was impossible, because they believed cells older than the embryonic stage lost the ability to produce a whole animal from a single cell.

Here's a short course on how Dolly came about:

Scientists took a cell from an adult sheep's udder. They took an unfertilized egg from a second sheep, and removed the part that contains its genetic code.

Next, the cell and the egg were zapped with electricity to combine them. The egg began dividing as a fertilized egg would divide, and became an embryo.

The embryo was implanted in a third sheep, a surrogate mother, that gave birth to Dolly. Aside from being genetically identical to the sheep that donated the udder cell, Dolly seems normal in every way.


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