Cover Story

A cloning glossary

The short course

Issue: "Cloning: Double trouble," March 7, 1998

In the current and coming debates, the devil will be in the definitions. So here's a rundown of the terminology we'll be grappling with. Clone: One individual (frog or sheep or mouse or human) created from a single cell of another individual, with exactly the same genetic makeup. It's been around for a while; what is significant-if true-about our most modern clone Dolly the sheep, is that she was cloned from an adult sheep's cell. Prior to Dolly, researchers were only successful in cloning from embryonic cells. Note: Think The Boys from Brazil, not Multiplicity. A clone of a person would be like a much-younger identical twin, not a carbon-copy similar in age and experiences. A clone of Michael Jordan would have his genetic gifts for athletics, but without a loving, attentive father to push him (such as Michael Jordan had), could that clone grow up to be an NBA star? Not necessarily. Nuclear transfer (also, somatic cell nuclear transfer): This is how Dolly is purported to have been created. Scientists removed the nucleus from an egg cell, and then replaced it with the nucleus from a cell from an adult sheep's udder. They then zapped the egg with electricity to jump-start it, and just like a fertilized egg, it grew into a whole new baby sheep (in this case, at least-there were 276 failures before they were successful with Dolly). Embryo: The very first stages of fetal development. Pre-embryo: There is no such thing. This is a made-up word being used by cloning researchers who want to distance their work from the abortion debates. If it's not even an embryo yet, what's wrong with experimenting on it? The Kennedy-Feinstein bill implicitly endorsed this view by contending an embryo isn't worth protecting until it is implanted in a woman's womb. Totipotent cells (also, stem cells): These are embryonic cells that have the potential to become anything-sort of like freshmen with undeclared majors. A totipotent cell could become a brain cell, or a bone cell, or a nose cell. Another definition for these cells is "gold mine." They're the real attraction for researchers right now. There's evidence they can be used to treat Parkinson's Disease and other illnesses; before now, the only source of these cells has been aborted fetuses. Transgenic: A transgenic clone is an individual organism with foreign genes. Scientists use transgenic sheep, for example, to produce medically useful proteins.

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