"The Supreme Court declared human genes unpatentable, but it didn't free the market for genetic testing.
In its decision, the Supreme Court maintained that man-made copies of human DNA were still patentable. These pieces are called cDNA, which are slightly altered copies of the naturally occurring genes. They are useful tools for genetic testing, since they can be used to relay a person's genetic information in a stable form. This bit of the ruling, in effect, allows Myriad to still lay claim to much of the breast-cancer testing.
Writing in Scientific American, Megan Krench, a geneticist, provides a more detailed answer (Reader's Digest version: While the Court took away Myriad's castle, they left them the moat):
Why do Myriad's patent rights to cDNA matter? There are several reasons. First, cDNA is an important research tool. For example, the edited cDNA sequence, not the longer DNA sequence, is often used to create animal models of diseases. Those models are essential for researching new treatments and cures. Without the licensing to BRCA1/2 cDNA, certain cancer research may be restricted to Myriad. Next, cDNA is critical for developing new diagnostic tests for genetic disorders. Since the BRCA1/2 genes themselves are not patented, it may be possible for other companies to develop new genetic tests—but the patented cDNA will make this process much more difficult."
Via Susan Zager