Medical diagnosis with Mutazyme

Thursday 25 February 2016

Medical diagnosis with Mutazyme

A cornerstone enzyme for error-prone PCR is Mutazyme, an enzyme with an increase error rate, but less biased than manganese mutagenesis. The manual is very clear and the only major annoyance is that it implicitly says that it makes 1.3 mutations per kb per cycle —that is the log2 of the fold amplification of the target—, whereas it actually makes something around 0.9 mutations per kb per cycle —even with the assumption that no DNA is lost during spin column purification or that DNA cut out of an agarose gel is not shockingly dirty.
However, the biggest mystery is that it says "Not for medical diagnostics".

I see three options:
  • Agilent lawyers are paranoid.
  • Agilent design team has a wickedly curious sense of humour.
  • There is a conspiracy theory afoot.
The first can be discarded, because most other PCR boxes do not have that rather ubiquitous disclaimer —I am pretty sure I once saw a microwave with it, but it might have been a transposed sticker. The second can also be discarded, because, well, the design of its small black box looks like a certain feminine hygiene product by Kotex. Therefore, there is conspiracy afoot: one can do crazy CSI stuff with it.
Obviously it was not used to amplify OJ Simpson's DNA as they did find a perfect match, but with EDTA —they must have used Phusion and actually eluted in TE and not water.So the question remains why on earth would one use a mutagenic PCR enzyme that costs more than Phusion in a diagnostic setting? The answer is simple: pretend there is more genetic diversity when there isn't. Specifically, when amplifying the DNA of clones strategically placed by some secret branch of the US government in collaboration with aliens... There you have it. The shocking truth.

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