NEW YORK — Companies and a university are moving to offer cheaper and broader genetic testing for breast cancer risk to a growing group of women, following a Supreme Court ruling that ended Myriad Genetics Inc.’s monopoly over DNA that vastly raises odds for the disease.

Within hours of the decision, the University of Washington and Ambry Genetics, a closely held company in Aliso Viejo, Calif., said they would immediately offer expanded testing that included the BRCA1 and BRCA2 genes, which Myriad has had under patent since the late 1990s. Quest Diagnostics Inc. said it would sell testing for the genes later this year.

By invalidating key parts of Myriad’s patents, the court has removed a bar that prevented labs using new technology from developing and selling broader one-time tests that search for all known cancer risks, including the BRCA genes, geneticists said. It could also mean lower prices for the screening, which can cost as much as $4,000 for Myriad’s most comprehensive version of its BRCA cancer gene test.

The decision “removes the barriers to comprehensive cancer genetic testing,” said Elizabeth Swisher, a gynecologic oncologist at the University of Washington in Seattle.

“For patients who have cancer or a strong family history of cancer, there is no reason you wouldn’t want to get the most comprehensive test available” that would scan all cancer risk genes in a single test, she said.

Faster, cheaper DNA testing is revolutionizing medical care. Nowhere has the impact been felt more strongly than in breast cancer. A woman who tests positive using Myriad’s tests carries as much as an 80 percent chance that she will get breast cancer in her lifetime. Testing helps women take charge of their medical future, providing options that can include preventive surgery and more extensive monitoring.

While 348,000 U.S. women carry at least one of the BRCA genes, fewer than 50,000 have been identified through testing, according to a 2012 study. With the publicity surrounding the Supreme Court case and actress Angelina Jolie’s May announcement that gene testing led to her double mastectomy, many doctors and genetic counselors say they have been flooded with calls from women asking whether they need to be tested.

The bad BRCA1 and BRCA2 genes, the most common cause of hereditary breast and ovarian cancer, are present in roughly 1 in 400 women and give women an elevated risk of ovarian cancer as well as a higher breast cancer risk.

As a result of the Supreme Court’s ruling Thursday, women can now undergo one-time testing for a wide band of genes that have been linked to breast and other cancers, said Mary-Claire King, the University of Washington geneticist who first proved that a single gene could vastly raise breast cancer risk, leading to the discovery of BRCA1.

That genes are products of nature and can’t be patented “has been the view of geneticists for a very long time and now it is the law of the land,” King said in a telephone interview. “I fully expect that many firms will enter this market.”

The U.S. Patent and Trademark Office issued a memorandum following the ruling that ordered its examiners to reject patent claims on isolated DNA, saying the high court ruling “significantly changes the office’s examination policy.” Further guidelines will be issued once the agency reviews the decision, according to the memo signed by Andrew Hirshfeld, deputy commissioner for patent examination policy.

While the University of Washington and Ambry previously sold DNA tests that evaluated a variety of genes linked to higher cancer risk, the screens couldn’t include the BRCA genes because of Myriad’s patents. Women who needed additional genetic testing beyond the BRCA1 and BRCA2 genes had to go through multiple rounds of often-expensive testing.

“As the leader in women’s health and cancer diagnostics, we are very interested in offering a BRCA testing service,” Wendy Bost, a spokeswoman for Quest Diagnostics, said in an email. “We now intend to validate and offer a BRCA1 and BRCA2 test service to physicians and patients later this year.”

Some quickly predicted that immediate competition for Myriad’s tests was unlikely, helping to boost the company’s shares. As more analysis of the decision was reported, the Salt Lake City-based company declined, ending Thursday 5.6 percent lower.

Last year, Myriad had $496 million in sales, largely from its tests for the two genes. The testing business carries an 87 percent gross profit margin, Myriad said in December.

“We don’t expect today’s decision to impact our business operations,” Ronald Rogers, a spokesman for Myriad, said Thursday in a telephone interview. The Supreme Court opinion doesn’t affect the vast majority of the company’s patent claims on the tests for the two breast cancer genes, he said.

“The remaining claims are valid and enforceable,” Rogers said, adding that Myriad offers “very high quality tests with fast turnaround times and good customer service.” The company also plans to start offering its own cancer-wide gene risk test this fall, which will analyze 25 genes that can put people at higher risk for various cancers.

Ambry, which is offering a basic form of its BRCA test for $2,200, posted a headline on its website soon after the decision saying, “Your Genes Have Been Freed.” The company also will include the BRCA genes for no extra cost in several broader based cancer risk tests it already offers.

At the same time, the closely held Gene By Gene Ltd., based in Houston, put out a statement saying it would offer BRCA testing for $995 in the U.S.

“Anyone who says it will take a while for companies to offer the test, or that it is uncertain that this ruling will lower the cost, we now have proof that it won’t take a while because it is happening as we speak,” said Sue Friedman, executive director of Facing Our Risk of Cancer Empowered, a nonprofit group that filed a brief in the Myriad patent case. “This will open up opportunity for other labs.”

The Supreme Court ruling and Jolie’s announcement in May that she had both of her breasts surgically removed to prevent cancer because she carries one of the BRCA genes will help democratize cancer genetic testing and bring in more at-risk patients for screening, doctors and genetic counselors said.

The developments have “put a light on an area of medicine that has really been under recognized for years,” said Ora Karp Gordon, director of the GenRISK Adult Genetics Program at Cedars-Sinai Medical Center in Los Angeles, in a telephone interview. “This is the most transformational, most monumental spring for the whole world of genetics and genetic testing.”

At Massachusetts General Hospital in Boston, the waiting list for a healthy woman to see a cancer genetic counselor has soared to five months from two months before the Jolie news, said Kristen Shannon, who leads a team of eight cancer genetic counselors at the Harvard-affiliated hospital.

The number of patient and doctor calls following the news about the actress was so overwhelming that the hospital sent a memo to all its affiliated primary-care doctors explaining which woman should be referred for testing, she said.

“This is what we had wanted for years but couldn’t generate the sustained interest,” Gordon said. “We did a lot of community outreach, but we just couldn’t get people to pay attention. Now we can’t keep up with the volume.”