BEAVERTON, Ore. – To most people, the word “mitochondria” is only dimly familiar, the answer to a test question in some bygone high-school biology class. But to Shoukhrat Mitalipov, the mysterious power producers inside every human cell are a lifelong obsession.

“My colleagues, they say I’m a ‘mitochondriac,’ that I only see this one thing,” he said recently in his modest, clutter-free office at Oregon Health and Science University. He smiled. “Maybe they are right.”

Mitalipov, 52, has shaken the field of genetics by perfecting a version of the world’s tiniest surgery: removing the nucleus from a human egg and placing it into another. In doing so, this Soviet-born scientist has drawn the ire of bioethicists and the scrutiny of federal regulators.

The procedure is intended to help women conceive children without passing on genetic defects in their cellular mitochondria. Such mutations are rare, but they can cause severe problems, including neurological damage, heart failure and blindness. About 1 in 4,000 babies in the United States is born with an inherited mitochondrial disease; there is no treatment, and few live into adulthood.

Mitochondria have their own sets of genes, inherited solely from mothers, and women who carry mitochondrial mutations are understandably eager to not pass them to their children. Mitalipov’s procedure would allow these women to bear children by placing the nucleus from the mother’s egg into a donor egg whose nucleus has been removed. The defective mitochondria, which float outside the nucleus in the egg’s cytoplasm, are left behind.

“It was a major breakthrough,” said Douglas C. Wallace, a professor of pathology and laboratory medicine at the University of Pennsylvania. “He’s an exceptionally talented person.”

But the resulting baby would carry genetic material from three parents – the mother, the host egg’s donor and the father – an outcome ethicists have deplored.

That specter drew critics from all over the country to a hotel in suburban Maryland late last month, where Mitalipov tried to convince a panel of experts convened by the Food and Drug Administration that the procedure, which he has pioneered in monkeys, was ready to test in people.

Some told the officials that the technique could introduce new genetic mutations into the human gene pool. Others warned that it could be used later for something ethically murkier – perhaps, said Marcy Darnovsky, executive director of the Center for Genetics and Society, “to engineer children with specific character traits.”

Back in his office, Mitalipov waved off those warnings. Mitochondrial DNA comprises just 37 genes, which direct the production of enzymes and molecules the cell needs for energy, he noted. They have nothing to do with traits like eye and hair color, which are encoded in the nucleus.

“There are always people trying to stir things up,” said Mitalipov, an American citizen who grew up in what is now Kazakhstan. “Many of them made their careers by criticizing me.”

The United States is not the only country weighing mitochondrial replacement. In Britain, the government has issued draft regulations that would govern clinical trials in people. If accepted into law by Parliament, such trials, which are how banned, would be allowed to go forward, although regulators would have to license any clinical application.