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June 13, 2013 | Posted By Ricki Lewis, PhD

Earlier today, my “in” box began to fill with info from everyone I’ve ever met letting me know that the Supreme Court had ruled on the Myriad case about patenting the breast cancer genes BRCA1 and BRCA2. I also received a dozen pitches from PR people offering me all manner of instant interviews with lawyers, doctors, bioethicists, and health care analysts.

No one offered me an interview with a geneticist – a person who knows something about DNA. So being such a person myself, I decided to take a look at the decision. And I found errors – starting right smack in the opening paragraph.

“Scientists can extract DNA from cells to isolate specific segments for study. They can also synthetically create exons-only strands of nucleotides known as composite DNA (cDNA). cDNA contains only the exons that occur in DNA, omitting the intervening exons.”

The definition is correct, the terminology, not. “cDNA” does not stand for “composite DNA.” It stands for “complementary DNA.”

cDNA came into fashion when I was in grad school, circa 1977. Like many genetics terms, it has a very precise meaning, something I pay attention to because I write human genetics books, including 10 editions of a textbook.

A cDNA is termed “complementary” because it is complementary in nucleotide base sequence to the messenger RNA (mRNA) that is made from the gene. Enzymes cut from the mRNA the sequences (introns) that do not encode amino acids and retains those (exons) that do encode protein. So a cDNA represents the part of a gene that is actually used to tell the cell to make protein. End of biology lesson.

A cDNA is created in the laboratory, and it is not a DNA sequence that occurs in nature. Hence, the Supreme Court’s part 2 of the decision, which acknowledges Myriad’s right to use a test based on a complementary, or cDNA.

I did a google search for “composite DNA” and just found the media parroting of today’s decision, and a few old forensics uses. So a caveat: my conclusion that the term is incorrect and invented is based on negative evidence. If I’m wrong, mea culpa in advance and I will feel like an idiot.

But cDNA isn’t the only error. I soon found another. On page 16, footnote #8 discusses a pseudogene as resulting from “random incorporation of fragments of cDNA.” That’s not even close to what a pseudogene is.

A pseudogene results from a DNA replication error that makes an extra copy of a gene. Over time, one copy mutates itself into a form that can’t do its job. The pseudogene remains in the genome like a ghost of a functional gene. The mutations occur at random because the pseudogene, not being used, isn’t subject to natural selection – that’s probably what the Court means by “random.” The globin gene locus on chromosome 11 is chock full of pseudogenes. This is such a classic example of basic genetics that my head is about to explode.

And how on earth is the Supreme Court’s definition of a pseudogene supposed to happen, in nature or otherwise? A cDNA exists in a lab dish. A gene exists in a cell that is part of an organism. How does the cDNA “randomly incorporate” itself inside the cell? Jump in from the dish? Part of the footnote states, “… given pseudogenes’ apparently random origins … ” Pseudogenes’ origins aren’t random at all. They happen in specific genes that tend to have repeats in the sequence, “confusing” the replication enzymes.

Today’s decision is undoubtedly a wonderful leap forward for patients, their families, and researchers. And some may think I am nitpicking. But these two errors jumped right out at me — I’d troll for more but I want to post this. What else is wrong? How can we trust the decision if the science is wrong? And what is the background of the people who research the decisions?

I know nothing about the law, zero, which is why I’m not writing about that. But the science in something as important as a Supreme Court decision should accurately use the language of the field under discussion.

This was first published on jUNE 13th on the PLOS blog.  Click here to read the original article.

Ricki Lewis is the author of "The Forever Fix: Gene Therapy and the Boy Who Saved It," St. Martin's Press, March 2012.  To read more blogs from the author, please visit her site at http://www.rickilewis.com.

The Alden March Bioethics Institute offers a Master of Science in Bioethics, a Doctorate of Professional Studies in Bioethics, and Graduate Certificates in Clinical Ethics and Clinical Ethics Consultation. For more information on AMBI's online graduate programs, please visit our website.

1 comments | Topics: Bioethics and the Law, Bioethics in the Media, Genetics, Government, Research Ethics

Comments

Robert Nussbaum,MD

Robert Nussbaum,MD wrote on 06/17/13 7:06 PM

Your identification of errors in the opinion is half correct. Yes, indeed,cDNA stands for complementary DNA, not composite DNA (whatever that means) just as you describe. However, there are two kinds of pseudogenes, processed and non-processed. Processed pseudogenes are partial or complete copies of mRNA, with the introns removed, that have been reverse transcribed into DNA courtesy of endogenous retroviral enzymes and inserted somewhat randomly throughout the genome. Their hallmark is that they lack intron sequences. The pseudogenes you describe are non-processed pseudogenes, are usually located near to the "real" genes they resemble and are indeed some kind of replication or recombination error that resulted in duplication of a gene, after which one of the copies will begin to accumulate mutations (if such mutations are not selected against), rending that copy non-functional and therefore a pseudogene.

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