Supreme Court bungles the science in DNA patent decision

[This is slightly modified from my post 2 days ago at Forbes.]

The Supreme Court ruled this week that Myriad Genetics doesn't own your DNA after all.  Myriad holds patents on the BRCA1 and BRCA2 genes, which are linked to an increased risk of breast and ovarian cancer, and they charge exorbitant fees for their DNA diagnostic test of those genes.  As I've written before (such as this 2012 Clinical Pharmacology article), Myriad didn't invent the genes, and the patents should not have been granted.  So in large part the Supreme Court got it right.

But they got the science wrong, as any geneticist reading today's decision will realize immediately. In the very first paragraph, they make no less than three errors of fact.  First, they write:

"The nucleotides that code for amino acids are 'exons,' and those that do not are 'introns.' "

Not correct.  Here's the facts: when making DNA into a protein, the cell copies DNA into RNA.  Big chunks of the RNA are spliced out and discarded.  Those are "introns."  What remains is "exons."  That's it.  The nucleotides that code for amino acids are contained within the exons, but they are not the same thing. It's not unusual for 25% or even 50% of the nucleotides in the exons to be ignored when stringing together amino acids to make a protein.

Error number 2 comes next, when the Court writes:

"They [scientists] can also synthetically create exons-only strands of nucleotides known as composite DNA (cDNA)."

Wrong again.  cDNA stands for complementary DNA, because the DNA produced is the complement of the original strand. This means that each nucleotide is replaced with its complement: A and T are complementary, and C and G are complementary.  The court gets this right later on in the ruling.

Just after this, they write:

"cDNA contains only the exons that occur in DNA, omitting the intervening introns."

Ouch! Wrong again.  cDNA simply means a complementary copy of DNA, which doesn't have anything to do with exons.  If you make a cDNA from a mature messenger RNA transcript, then yes, it will contain only the exons.  But you can make cDNA from other parts of the genome, and from other types of RNA transcripts.

There are more errors further down in the decision. For example, they write that "Nucleotides that do not code for amino acids, in contrast, are known as 'introns.' "  This just compounds one of the errors above.  They also used the term "pre-RNA" instead of the correct term "pre-mRNA."  I could go on.

It's troubling that the highest court in the land can't get even the basic facts of molecular biology right when writing a decision that has such fundamental importance to genetic testing, the biotechnology industry, and health care.  I cannot pretend to know who they got to do their biology background research, but any genetics graduate student could have done far better.