In a unanimous decision last month, the Supreme Court ruled that naturally occurring genes are not patentable. But, said the Court, cDNA, a man-made copy of the genetic messenger in cells, is patentable. As a geneticist, I have my own opinions about this ruling. But the potential outcomes are important enough that all members of the public, not just biologists, should be equipped with the knowledge to evaluate it. The ruling may significantly affect patients’ access to genetic testing, and it sets an important precedent for future developments in the biotechnology sector.
The company that applied for these patents is Myriad Genetics. Building on the work of researchers around the world, Myriad identified the location and sequence of two genes that are sometimes mutated in breast cancer, known as BRCA1 and BRCA2 (collectively, BRCA1/2). Myriad filed patents for the genes in 1994 and 1995.
People can have their risk of breast or ovarian cancer assessed by finding out if they have mutations in BRCA1/2. Then, one can use this information to increase preventative care measures, like increased screening, or even having both breasts completely removed (a double mastectomy)--an elective surgery recently made famous by Angelina Jolie.
Myriad Genetics is the primary distributor of the BRCA1/2 test, which costs upwards of $3000. Because Myriad owned the patents on BRCA1/2, it was the only company that could administer the test for cancerous mutations.
The Supreme Court ruled that genes cannot be patented because "natural phenomena" are not patentable. That’s good news for doctors, researchers, and anyone who doesn’t like the idea of a company owning patent rights to pieces of your body. It also opens up BRCA1/2 testing to labs other than Myriad. But, the Court also ruled that cDNA, an edited man-made copy of the gene, can be patented. Ruling that cDNA can be patented will have important consequences for research, including research to discover new disease treatments and create new genetic tests.
Few people outside of biology research have heard of cDNA. In order to understand the critical distinction between DNA and cDNA, some background is necessary. Genes, which are made of DNA, contain the information required to make proteins. DNA is double-stranded, like a ladder. The familiar DNA nucleotides A, C, T, and G each have a complementary partner they always pair with: A always pairs with T, and C with G.
To make protein from DNA, several steps must happen (illustrated in the accompanying schematic). First, the DNA pulls apart into two separate strands and a copy is made. Instead of DNA, this copy is made of RNA. The copy, called pre-RNA, is not identical to template DNA. It’s a complementary copy. Next, that pre-RNA is edited so that only the parts that encode protein (the exons) remain. This exons-only version is called mRNA. The cell then uses the mRNA to assemble proteins.
For scientists, working with RNA is difficult; it is unstable and degrades quickly. So it is sometimes advantageous for researchers to extract mRNA and convert it back to stable DNA. The new DNA that’s created from the mRNA is called cDNA (see DNA to cDNA schematic). Just like pre-RNA is a complementary copy of the DNA template, the cDNA is a complementary copy of the mRNA template. It’s worth mentioning that cDNA can occur naturally; certain viruses can copy mRNA to cDNA (in fact, this is where scientists learned the technique).
