[JosephBrown]

An mRNA strand that is about to be translated into a protein has the introns removed, so how is the cDNA different enough from the naturally occurring mRNA other than it is a mirror image?

Also, when did cDNA come to mean composite DNA instead of complementary DNA? This seems made up to imply some kind of invention instead of it just being the mirror image of the DNA molecule.

[rcthompson]

It doesn't matter that cDNA is similar to something found in nature. The fact is that DNA complementary to the mature spliced mRNA sequences of the BRCA1/2 genes does not exist in nature.

[mokus]

This really sounds like hair splitting to me. Along the lines of saying "well, your software patent is for a program that is stored on a GMR disk platter. Mine's stored in NAND flash, and that's never been done before!"

If the sequence is logically equivalent but stored on a different medium, how is that novel? The invention of the new medium or new techniques for transcribing between media may be, but the sequence itself isn't.

[rcthompson]

Not exactly. DNA and RNA are structurally only slightly different, but functionally, in the context of a biological system, they are very different. A technical analogy might be RAM vs disk.

[dekhn]

wrong. this happens in retroviral transmission all the time.

[rcthompson]

To my knowledge, the BRCA1 mature mRNA sequence has not been shown to be reverse-transcribed during any part of the life cycle of any retrovirus.

[dekhn]

given that retroviruses are sloppy, basically any any all genes have at some time been reverse transcribed.

[rcthompson]

True, but that's a tenuous argument. You can't prove that a particular gene has been reverse transcribed and that its cDNA is therefore a naturally-occurring product, unless that cDNA is essential to the virus' life cycle. To invalidate the patent, you would probably have to actually observe the natural reverse transcription of the complete sequence.

In any case, the original point I was trying to make was that the natural occurrence of the mRNA does not make the cDNA a naturally occurring product.

[polyfractal]

It is probably more accurate to say that cDNA represents a snapshot in time of a particular mRNA "species". Any particular mRNA could lead different lives, depending on what kind of post-translational modifications are made to it (e.g. different proteins editing the mRNA differently before it is eventually transcribed).

So any particular mRNA might actually have several different products, or may just get chopped up into shRNA or microRNA.

[rflrob]

I am a biologist (who regularly sequences cDNA), and it is properly understood to mean complementary DNA. In fact, the syllabus' description of the process is far enough from what the process of actually making cDNA is like that it seems to me there could be grounds for a challenge, even though as others have noted, cDNA is no longer widely used for these kinds of diagnostics.

[michaelhoffman]

The syllabus is not part of the decision and has no legal effect (it says this at the top of every syllabus), so wouldn't be grounds for a challenge.

http://en.wikipedia.org/wiki/United_States_v._Detroit_Timber...