A prominent geneticist shifted the debate over a controversial anti-abortion bill yesterday by claiming the measure would end prenatal diagnosis of deformed fetuses and outlaw some birth control pills and intrauterine devices.

Claiming the bill is "fundamentally counter to the best interest of the people," Dr. Leon E. Rosenberg, chairman of the Human Genetics Department at the Yale Univeristy School of Medicine, sharply criticized seven witnesses who had testified before him for allowing their "religious feelings" and "personal biases" cloud their professional judgments.

All seven voiced support for the bill's central thesis: that "scientific evidence indicates a significant likelihood that actual human life exists from conception."

"I know of no scientific evidence which bears on the question of when actual human life exists," said Rosenberg, appearing during the second day of hearings on the measure. "I believe that the notion embodied in the phrase 'actual human life' is not a scientific one, but rather a religious metaphysical one.

"This bill, if enacted into law, will prohibit the use of wuch commonly employed contraceptives as the intrauterine devices [IUDs] because they prevent uterine implantation and, thereby, act against the fertilized ovum which has, by legal decree, been made a person," Rosenberg told the Senate Judiciary subcommitte on separation of powers.

It would also stop all amniocentesis -- prenatal tests used to determine the health of the fetus, particularly in pregnant women over 35, he said. The tests are used to look for deformities and genetic disorders like anencephaly (congenital absence of all or part of the brain) or Tay-Sachs disease.

He argued that, despite what the seven scientific witnesses had testified, "a great majority of clinicians and scientists in this country would support my side of the argument."

Rosenberg was greeted with loud applaouse when he finished testifying, and Sen. John East (R-N.C.), who chaired the hearings, conceded, "You have a valid point." East, who has been accused on conducting a one-sided inquiry into the abortion issue, took special pains to point out repeatedly that he intends to conduct long and exhaustive hearings on the bill, into the summer months.

This represents a drastic shift in strategy. East, one of the most outspoken new conservatives in Congress, had originally hoped to hold just two sets of hearings, dealing only with scientific and legal arguments on the bill, which would allow states to outlaw abortion.

Even if the bill passes, he added, "it will not end the debate on abortion. It is a major policy question that will be with us an indefinite period of time. We are not at Armageddon here."

Rosenberg's testimony was disputed by Dr. Alfred M. Bongiovanni, professor of pediatrics and obstetrics at at the University of Pennsylvania, and Dr. Jasper F. Williams, a Chicago physician and former president of the National Medical Association.

"I have learned since my earliest medical education that human life begins at the time of conception," said Bongiovannia, a Roman Catholic and long-time opponent of legalized abortions. Five distinguished physicians offered similar testimony in the first raucous day of hearings Thursday when six women were arrested for disruptions.

Williams, upset by Rosenberg's charges, declared his view that human life begins at conception, is "not narrowly based on religion."

East pressed Rosenberg on when he would begin to protect life. The Yale professor replied, "at the point of viability, at the point the human being can exist on its own outside the uterus."

Bongiovannia, however, noted the medical definition of viability "changes every three or four years."