Myriad Genetics offers a test which lets women know whether they are at increased risk for breast cancer. The test tells women whether they have BRCA gene mutations. Women with these mutations are up to 65% more likely to develop breast or ovarian cancer. Myriad's patent covered ANY use of the mutations including ANY OTHER test for those mutations. Although Myriad claimed to allow further scientific research on these mutations, it isn't clear that they actually allowed all research to go forward. More importantly, Myriad used the patent to block all competitors from introducing other (different) tests. Patients who couldn't afford the tests had no other option. Even those who could afford the tests had to option to get a second opinion (important as no tests are fool-proof).
SCOTUS ruled today quite rightly that patents cannot cover naturally occurring genes. SCOTUS has drawn some fairly bright lines this year. Past cases have shown that patents of human transplanted genes are valid and those patents. The ruling earlier this year on the replanting of Roundup Ready Soybeans shows that those patents are broadly enforceable. This ruling shows that patents of naturally occurring genes are not valid. Note that in the Roundup Ready Soybean case, the genes in question did occur naturally, but were transplanted from a bacterium into soybeans.