In what is being ballyhooed as a landmark decision likely to set the course of DNA-based diagnostic and therapeutic medicine for the next several decades, the US Supreme Court unanimously decided on June 13 that human genes are not patentable. Rather than objects invented or discovered, human genes are henceforth to be treated as "naturally occurring phenomena," and hence fail the patentability test under 35 USC 101. As is usual in patent cases, however, the ruling contains delicate shades of meaning.

An obvious question concerns why the Supreme Court limited its decision only to human genes. The immediate reason is that the patents under review pertained only to human genes. However, the science is essentially the same in all eukaryotic organisms, that is, in all organisms whose cells are encompassed by a membrane, and which contain DNA-based genes (usually) confined within a cellular nucleus. Essentially all multicellular organisms are formed of eukaryotic cells. Accordingly, it is likely that the new rules regulating patenting aspects of human genetic codes will apply to multicellular organisms in general, although that is not yet established legally.

In particular, the Supreme Court's opinion, written by Justice Clarence Thomas (who has made the science relating to the decision extraordinarily clear), nowhere made note of any "special" status of humans as compared to other animals. It is amusing, however, to report that Justice Scalia, although concurring with the judgment, felt it necessary to note in reference to the testimony concerning molecular biology that he is "unable to affirm those details on my own knowledge or even my own belief."

Is "naturally occurring" far-reaching enough?

According to yesterday's Supreme Court decision, any genetic material or protein that is made through the process of gene expression is "found in nature," and is not patentable.
Gene expression is the process by which genetic information is used to create a working gene product, such as RNA or a protein. A process of isolating and purifying such a material might be patentable, and applications not found in nature for such a material might be patentable, but the material itself is not.

As it happens, there are large areas of diagnostic and therapeutic genetic medicine in which the form in which the genetic material is actually used is complementary DNA (cDNA). This is a DNA strand from which all the introns, which are non-coding sections of DNA, have been removed by RNA splicing during gene expression. When the original DNA is from a living source, the corresponding cDNA is never formed in nature. As a result, cDNA was declared patentable by the Supreme Court, provided that the other requirements for patentability have been met.

Well, is cDNA useful for anything? Beyond doubt. Nearly any application in which one would use human DNA can be achieved using human-based cDNA. If you want to insert a gene from an advanced organism into a bacterium, you cannot use the original form of the DNA, because bacteria lack the ability to remove introns when their genes are expressed. Instead, you insert cDNA into the bacteria, as all introns have been excised from the cDNA version of the gene.

Complementary DNA is often used in gene cloning, as gene probes, or in forming an exon library. (Exons, unlike introns, are biologically active sections of DNA that remain present within the final mature RNA product.) In general, working with cDNA is potentially less confusing to both the cells being modified and to the biologists. Similarly, when amplifying DNA sequences, a combination of reverse transcription followed by the Polymerase Chain Reaction (PCR) is used to form cDNA sequences with which to simplify further analysis.

As so often happens, the Supreme Court has tried to draw a clear line in the sand with a feather duster. Human genes, the materials that appear in the process of gene expression, and the end proteins for which they code are no longer patentable, which is good. However, in nearly all present cases of commercially important processes, the cDNA on which they are based is patentable, even though it contains the identical genetic instructions. Still, one is "natural," and the other would not exist save for a biochemist in a laboratory.

Perhaps someday the legal world will take notice of the concept of a gene as biologically coded information, which would make cDNA based on eukaryotic DNA unpatentable, erasing the idea that other people can own your genetic information. That day is not yet here.