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Science, says Rabbi Moshe Tendler, has made him a liar.

"For so many decades, I'd been teaching the one-gene, one-enzyme axiom of biochemistry," recalled Tendler, a biblical scholar and biology professor at New York's Yeshiva University. "I taught there were around 100,000 genes. Over the weekend we lost 70,000 genes. And one gene has suddenly learned to make multiple enzymes."

Tendler's biology students "will not take this lightly. I'm embarrassed to go back to school," he said Sunday, speaking at the 11th International Conference on Jewish Medical Ethics in Burlingame. "It's a pleasure to teach talmudic law from 9 to 3. Then I put on a lab coat and become a liar."

The recent advances in genomics that Tendler referred to may have helped make him "a liar," but they have not ignited nearly as much of a firestorm as the subject of stem-cell research, which was the focus of his talk.

It is stem cells' variability that gets scientists so excited. Within the body, the same stem cell can develop into a nerve cell; a muscle, liver or blood cell; or perhaps even a bone or pancreatic islet cell. Scientists' ability to harness the full power of stem cells could lead to breakthroughs in the treatment of Parkinson's disease, muscular dystrophy, cardiac disease, liver failure, diabetes, anemia, leukemia and osteoporosis, to name just a few afflictions.

Ethical concerns, however, have thrown roadblocks in the way of stem-cell research. Some religious groups claim that the death of an embryo in the petri dish is tantamount to abortion — which, they contend, is tantamount to murder.

"It is the power of the Catholic Church that has held back embryonic research for decades. We concur with the Catholics that abortion is murder — but not from a petri plate. Abortion is murder when you take it out of a woman. But an egg, sperm and zygote lying in a petri plate, that never saw the inside of a woman, that was not born of woman?" Tendler questioned.

"But the power of the church is so great as to hold back 'petri plate abortions' all these years. This is no minor concern," added Tendler, who, between serious points, kept the audience of several hundred giddy with numerous jokes and anecdotes. "I speak now as a Jew who is a proud American. I have a boast neither Bush nor Clinton can make — I have great-grandchildren who are sixth-generation Americans. I'm a real Yankee. It concerns me when a politician gets up and says, 'This is a Christian country.' I wasn't aware of that."

Tendler said it would be "inhumane" not to foster research that could save human lives and heal the disabled.

"We should not cure my neighbor the paraplegic because it's against religion?" he asked. "Whose religion?"

In the United States, all human embryological research is prohibited from receiving public funding. Yet there is no prohibition of private corporations bankrolling such research, a practice that Tendler and University of Toronto geneticist Janet Rossant, another featured speaker, opposed.

"What this leads to is probably the worst of all worlds," said Rossant, a professor of molecular and medical genetics. "Since the research can take place in the private domain and, in this country, has essentially been derived with private money…this leads to a potential conflict between public good and private profit."

Perhaps the best-known example of stem-cell technology was the successful cloning of Dolly the sheep. The Scottish researchers' feat shattered scientists' beliefs in the impossibility of mammalian cloning and was interpreted by non-scientists around the world as a transformation of science fiction into science fact.

Yet, at the conference, both Tendler and Rossant characterized Dolly-like endeavors in cloning as frivolous science and a distraction from the incredible medical benefits that could be reaped from stem-cell research.

"So someone pulls off a Dolly. So what? Who cares?" asked Tendler. "Who's concerned that people will run around reproducing themselves? One or two kooks in the world are interested in that."

Continuing in a tongue-in-cheek mode, Tendler added: "Nobody is interested in cloning and there ain't no money in it. The money and glory is in repairing organs."

While he is an ardent supporter of stem-cell research, Tendler pointed out that the possible consequences of scientists learning to regenerate failing organs might lead to ethical quandaries down the road.

Responding to an article in Science magazine in which the possibility of immortal life and forced euthanasia was bandied about, the rabbi said such a development would blur the line between man and God.

If humans achieved immortality, he said, "Grandparents would be competing for the same jobs with their grandchildren. This cannot be. So we would have to set some kind of standard as to when your inning is up.

"This is where biblical ethics steps in and says, 'Hold up, fellas.' You forgot — you're humans, not God. You're not in charge of this world."

Jews, said Tendler, "are not afraid of immortality. We have no problem. That's God's problem. What are you doing mixing into God's business?"