Clip_31Ever since she tested positive for a defective gene that causes breast cancer, Tamar Modiano has harbored a mother’s fear: that she had passed it on to her two daughters. Ms. Modiano had her breasts removed at 47 to prevent the disease and said that the day she found out her older daughter tested negative was one of the happiest of her life.

Now she wants her younger daughter, Hadas, 24, to be tested so she can start a family early if she is positive and then have a double mastectomy too. Ms. Modiano’s elder daughter, Suzi Gattegno, 29, disagrees.

“You’re keeping her from living her life,” Ms. Gattegno told her mother. “You want to marry her off early.”

“If she’s a carrier, she should marry early,” her mother countered.

“She doesn’t even have a boyfriend,” the daughter said. “You need to stop pressuring her.”

“I want to protect her!” Ms. Modiano replied.

Such family debates are playing out across Israel these days. The country has one of the highest rates of breast cancer in the world, according to a World Health Organization report. And some leading scientists here are advocating what may be the first national screening campaign to test women for cancer-causing genetic mutations common among Jews — tests that are already forcing young women to make agonizing choices about what they want to know, when they want to know it and what to do with the information.

The so-called Jewish breast cancer genes have preoccupied women here for years, but after the actress Angelina Jolie revealed in May that she had undergone a double mastectomy because she had tested positive for such a mutation, coverage here exploded, with radio and TV talk shows featuring Israeli women grappling with similar decisions.

Jews of Ashkenazi, or central and eastern European, backgrounds, who make up about half the Jews in Israel and the vast majority of those in the United States, are much more likely to carry mutations that increase the risks for both breast and ovarian cancers, according to the National Cancer Institute.

A number of influential geneticists and cancer doctors from various medical centers here say that the Israeli Health Ministry should pay for free voluntary genetic testing of all Ashkenazi women over the age of 25. About a million women would be covered, at a cost of less than $100 per test. Jews of Iraqi descent, whose families also often carry a harmful mutation, might also be screened.

The goal of a proposed universal screening program would be to identify an estimated 30,000 Israeli women who have the mutations. So far, with sporadic testing, about 6,000 of them have been found, many only after a cancer diagnosis, said Dr. Ephrat Levy-Lahad, the coordinator of the Israel Genetics Consortium.

“That’s our target population,” said Dr. Oded Olsha, a breast surgeon at Shaare Zedek Medical Center in Jerusalem. “If we can find them, we can save their lives.”

Women who tested positive for mutations in the BRCA1 and BRCA2 genes, which suppress tumors, would be strongly encouraged to complete child bearing by their late 30s so they could have their ovaries removed by age 40. Risk-reducing mastectomies would also be offered.