4 ms·
PCR is a basic tool. It amplifies, much like your car stereo. If you can hear music when tuning in an AM station, you don’t question the automatic gain correcti
by blackguardx 2y ago
PCR is a basic tool. It amplifies, much like your car stereo. If you can hear music when tuning in an AM station, you don’t question the automatic gain correction the stereo is doing internally. PCR is the same way. If the target is present, it is detectable. If it isn’t then it isn’t. There are so many variables at play that the number of cycles isn’t very meaningful.
- tanseydavid 2y agoKary Mullis, inventor of PCR does not agree with your analogy.
- churchturing 2y agoHe also * believed in astrology * denied Avogadro’s number (???) * practiced telepathy * didn’t believe in HIV causing AIDs * didn’t believe in climate change * didn’t believe in the ozone hole While he certainly had incredible intelligence, clearly him believing something isn’t a hugely convincing reasoning. disclaimer: i am a person who believes in Avogadro’s number and not astrology. truly an intellectual outcast and rebel
- dekhn 2y agohe didn't deny avogadro's number so much as say that its definition was somewhat arbitrary. IIRC he made the comment before the modern redefinition of SI units. See https://en.wikipedia.org/wiki/2019_revision_of_the_SI#Mass_and_the_Avogadro_constant https://en.wikipedia.org/wiki/2019_revision_of_the_SI#Mass_a... for more details about the ongoing issues associated with absolute numeric counts of elements and their association with mass.
- churchturing 2y agothis is useful context, thanks. would edit my prior comment but it is no longer editable. after some more research it seems his comments on the matter were reasonable
- blackguardx 2y agoCan you expand on this? What does he not agree with?
- aftbit 2y agoIs sample contamination more impactful (likely to lead to a false positive) at 100 or 200 cycles than at 20? I remember some distrust of high PCR cycle counts during COVID but I never quite understood the fear.
- blackguardx 2y agoIf there is contamination with the target sequence then it will be found by the PCR analysis. I don’t know the practical limits of sensitivity but theoretically it can detect a single occurrence of the target sequence.
- Izkata 2y agoWith enough cycles, dead virus you're successfully fighting off can be detected. It doesn't need contamination. For what it was used for, those were false positives that inflated the counts.
- timewizard 2y agoYou run PCR for cycles. You run it for 32 cycles? You've got a 4 billion times multiplication of the input signal. You see the problem? "Detectable" isn't a single ended specification with "PCR." You really do need to disclose how many cycles you ran. Similarly there's ionizing radiation in your home. Right now. Flowing through you. If it's not above the background it's not interesting or material. So just saying "we found radiation" is equally meaningless unless you tell me that level in relation to something.
- mharig 2y ago[dead]