Animal reproductive cloning, on the other hand, seems to be less concerting to most. Dolly the sheep was cloned by the Scottish Roslin Institute and PPL Therapeutics in 1997. Other species cloned through the science are cattle, goats, rabbits, cats, pigs and horses. Hwang and his colleagues reported in the Aug. 4, 2005, issue of Nature that his group had cloned the world's first dog, an Afghan hound named "Snuppy" - Seoul National University puppy. And on Sept. 1, biotechnology companies ViaGen Inc., of Austin, Texas, and Encore Genetics Ltd., of Weatherford, Texas, announced that they have cloned six "high-profile performance horses" - the first commercially cloned horses in the U.S.

As the range of species that can be cloned has expanded, so have the purposes they are cloned for. As those purposes differ, so does the ethical defensibility of the act. Those engaged in animal cloning for medical purposes are quick to point out that they have a higher calling than those charging bereaved pet owners tens of thousands of dollars for a genetically resurrected animal. Gerald Schatten, professor of obstetrics, gynecology and reproductive sciences and cell biology and physiology at the University of Pittsburgh Medical School and part of the team involved in cloning Snuppy, has been widely quoted for his tart remark: "We are not in the business of cloning pets."

Bioethicists agree that cloning for medical purposes is ethically distinct from cloning to recreate either commercially valuable animals or beloved pets. Laurie Zoloth, professor of medical ethics and humanities and of religion at Northwestern University's Feinberg School of Medicine, told BioWorld Today that the discussion around ethical differences between cloning animals "is a lot like the treatment vs. enhancement issue in humans." Genetic manipulation for treating life-threatening diseases is seen as ethically justifiable and a laudable goal, but although humans routinely try to enhance themselves using everything from espresso to plastic surgery, "we get uneasy when the words genetics and enhancement are used in the same sentence," Zoloth said.

In the same way, "when we talk about cloning to save the life of a species that might otherwise be utterly destroyed, that seems worthy," Zoloth said. But "when we move over to wanting your pet cloned, pretty much everyone thinks of that as a narcissistic or trivial use of the technology."

Somewhere in between heroics and narcissism lies the cloning of farm animals and plants. Here, a second ethical issue comes into play: Zoloth pointed out that many people are uneasy with the use of nontraditional technologies to alter animals and plants. That's despite the fact that "people have been using biotechnology to manipulate how a species turns out pretty much since the iron age."

She pointed to biblical accounts of making flocks of spotted sheep and goats for the Hebrew patriarch Jacob. And Zoloth added that in terms of animal suffering, classical breeding also is ethically problematic. She particularly pointed to the breeding of dog species, many of which are prone to health problems because of reproduction programs taken to extremes, with no cloning involved.

"If you look at the safety and comfort of the animal, a lot of [ethically problematic] things have already been done," Zoloth said. She does not believe that there is a significant difference in and of itself between genetic manipulation via breeding vs. cloning. "To look at this as less natural than dog breeding is, I believe, a conceptual error," she said.

Friday's article will focus on the science of animal cloning.