Genetic tests for cancer can run thousands of dollars, but Color Genomics plans to change that: it's offering testing for the cancer risk variants BRCA1 and BRCA2 — as well as 17 others — for $249, starting today. By comparison, Myriad Genetics' similar test costs about $4,000.

Unlike consumer-oriented genetic testing offered by 23andMe, Color Genomics' test will be available only through health care providers. And the company has genetic counselors available to help patients interpret their results. It's a major challenge to Myriad's BRCA empire, at a fraction of the cost, just as insurers begin to shy away from the bills for genetic testing.

The gene variants BRCA1 and BRCA2 are among the best-known risk factors. Carriers of BRCA1 have an 80 percent risk of developing breast cancer and a 50 percent risk of ovarian cancer before the age of 80. Women with family histories of cancer — including, most publicly, Angelina Jolie and Masha Gessen — have written about taking the test, and choosing to receive preventive mastectomies, to dodge their genetic risks.

The Supreme Court ruled two years ago that human genes can't be patented Myriad has faced widespread criticism over the cost of its tests, though the company says that insurers typically pay the bulk of the expense. Color Genomics' test isn't going to be reimbursed by insurers, says Elad Gil, a co-founder of Color Genomics. That's why its price is so much lower — people have to be willing to pay for it on their own. Gil says that Color Genomics has lowered the costs by automating more processes, like taking a family history and working with variant interpretation. Color Genomics' test complies with the standards used by most makers of genetic tests.

Color's test wouldn't be possible if the Supreme Court hadn't ruled two years ago that Myriad couldn't hold exclusive rights to BRCA testing because human genes can't be patented. Myriad — which currently accounts for 90 percent of the heredity testing market for cancer, according to Reuters — will probably face more challenges from low-cost competitors like Color in the coming years. Last month, Goldman Sachs Myriad's rating to "sell," citing increasing competition in genetic testing.