What is a PCR test, who invented it and why should we care?

February 19, 2021

Since the beginning of last year, most people have heard of PCR. But what is it, how does it work and can we trust it?

When DNA research was in its infancy, doing meaningful tests on specific DNA was a time-consuming affair. To replicate any DNA was a shot in the dark with very unpredictable and unreliable outcome.

When Polymerase Chain Reaction was invented, in 1983, it substantially changed the landscape of molecular biology (the field that deals with biology on the DNA and RNA level). Now it was possible for scientists to take a very small sample of DNA and amplify it rapidly, creating copies ‘exponentially’ at every cycle.

In laymen’s terms, what it does is split the required DNA strand in half, and uses a polymerase, which is an enzyme that synthesizes nucleic acids (the building blocks of DNA and RNA), to turn the split strand into two copies of the original.

The aim is to double the output at every step.

This invention made it possible for the scientists to do research on any kind of DNA and RNA regardless of how big their original sample was. The technique has been so instrumental in the field of molecular biology that the inventor, Kary Mullis, received a Nobel prize for his work (1)

Who is Kary Mullis, and does it matter?

It is easy to say that Kary Mullis is not the usual scientist. A brief look at some of the things he is quoted as saying seem to reveal a person who has strong views and few inhibitions to express them. (2)

He was a vocal advocate against PCR being used as a diagnostic tool. He was particularly concerned by people being diagnosed with having HIV through the use of PCR.

His argument was that PCR is simply a tool that allows scientists to generate a large number of copies of any type of DNA or RNA.

“It’s just a process used to make a whole lot of something out of something. That’s what it is. It doesn’t tell you that you’re sick and it doesn’t tell you that the thing you ended up with was going to hurt you or anything like that.” (3)

He has, to some extent, been vilified by people in the industry for his unapologetic stance on what he saw as misuse of PCR. More recently, after his death in 2019, his Wikipedia entry was updated, putting his credentials and academic achievements into question. (4)

The edits were very specifically taken from an interview published by UC Berkeley’s Cal Alumni online magazine. In the interview, Tom White, a former Berkeley classmate and colleague at Cetus Corp where Mullis invented PCR, seems to have a personal agenda and speaks in vindictive terms about Mullis.

Whether or not the claims are correct, or relevant, Tom White admits to have personal issues with Mullis, and the article itself was published after his death. (5)

In an earlier version of his Wikipedia page, prior to April 2020, very few negative remarks are visible. It is in the post April 2020 version that we read:

“he struggled to pass his oral exams (with a colleague recalling that “he didn’t know general biochemistry”), and his dissertation was only accepted after several friends pitched in to “cut all the whacko stuff out of it” while his advisor lobbied the committee to reconsider its initial decision. “

The post April version seems to focus on any potential smear of Mullis’ character. Whether or not this is in relation to the fact that many people started to question the use of PCR around this time, many of whom referred to Mullis’ vocal criticism, we shall never know. Yet the timing is remarkable, to say the least. (6)

So why should we question PCR?

PCR works with cycles. For every cycle, the DNA or RNA is heated up, which is what splits the strand. Heat resistant polymerase is used to turn the split strand into two copies or the original, after which the cycle repeats.

This is an exponential amplification. One becomes two, becomes four, eight, etc. This is very useful if you are trying to amass enough sample to do all sorts of tests and studies on. For even with a single strand of DNA or RNA, after as little as 30 cycles, you can have 536,870,911 copies.

Push this number of cycles up to 40 and you will end up with a total of 549,755,813,888 from a single strand.

Contrary to what many people believe, viruses reside in all of us. Through our immune system we have a constant cleansing of our body going on at all time. A single virus does not make you sick. Once a pathogen is detected, a signal is sent and our immune system is put into action. (7)(8)

PCR Cycle threshold.

The PCR tests for Covid contain a medium that adds colour to the ‘desired’ RNA, which will then become either visible or not. The number of cycles at which you test ‘positive’ is referred to as the Cycle threshold (PCR Ct). It is accepted science that the higher the PCR Ct number, the less infectious a person is, if at all. Despite this fact, PCR tests are not reported with the PCR Ct number recorded.

Although it has been confirmed by various scientists, the WHO and even some of the top level decision makers in Public Health that the number of cycles is significant to the validity of the test, very little has been done to raise public awareness or to address any of the issues. (9)(10)

Dr. Anthony Fauci is an American physician-scientist and immunologist serving as the director of the National Institute of Allergy and Infectious Diseases since 1984 and chief medical advisor to President Joe Biden since 2021.

There is a recording on July 16 of the podcast This Week in Virology, episode 641, in which Dr. Fauci addresses some of the controversy surrounding PCR. When asked about the PCR and Cycle threshold he seems to dismiss the value of a positive test over 35 cycles.

“What is now sort of evolving into a bit of a standard, that if you get a Cycle threshold of 35 or more, that the chances of it being replication-competent are miniscule. If someone comes in with 37, 38.. even 36 you’ve got to say, you know, it’s just dead nucleotides, period.” (11)

To translate, in case it wasn’t already obvious, if a virus is not replication-competent this means it is not transmissible. This means that a positive test over 35 cycles does not make you infectious. Dead nucleotides is Dr. Fauci’s way of saying that the measured RNA is inactive and unable to cause illness or infect anybody.

When asked if reporting the Cycle threshold number is standard practice in Covid testing, Dr. Fauci responds:

“…if somebody comes in and it’s positive, they don’t give them the threshold until you go back and ask for it.” (11)

In the podcast immediately preceding (episode 640), Dr. Michael Mina, an Assistant Professor of Epidemiology at Harvard T. H. Chan School of Public Health and a core member of the Center for Communicable Disease Dynamics (CCDD), also explains that people who test positive at 40 are not likely to be transmitting the disease and have probably not transmitted it for a number of days already. He says that people who transmit the disease are showing up as positive below 30 or even 25 cycles, with one having tested positive as low as 8 cycles. (12)

There are numerous reports of Covid tests routinely being done at 40 or more cycles. The Guidance section on the gov.uk website has a document called ‘Understanding Cycle Threshold (Ct) in SARS-CoV-2 RT-PCR” in which they state: “A typical RT-PCR assay will have a maximum of 40 thermal cycles” (10)


Once you understand the basic principle of PCR, and you know the fact that it’s not uncommon to carry a host of different virus strands, without being sick or in danger of becoming sick, it is easy to see that with a sufficient number of cycles, it is almost impossible for the test to come out negative.

We have now seen that Cycle Threshold is not routinely reported. The public is largely kept unaware of the significance of this data and many test centres are not even aware this is problematic. Even the general recommendations from Public Health England’s guidance do not actively caution against running PCR tests as many as 40 cycles.

Unfortunately, it seems we cannot blindly trust science to do the right thing. Many scientists are simply following instructions, some knowingly but most without any idea of what they’re doing. We need to make sure we are educating ourselves and each other. In the end, a lab coat does not make you a better human, a positive PCR test doesn’t make you a bio-terrorist.

Written By Mik Witkamp

(1) Wikipedia: Polymerase Chain Reaction

(2) BrainyQuote: Kary Mullis Quotes

(3) Internet Archive Kary Mullis Speaks To Misuse Of PCR (1993)

(4) Wikipedia: Kary Mullis

(5) Intolerable Genius: Berkeley’s Most Controversial Nobel Laureate

(6) Wikipedia: Kary Mullis (version 18:13, 26 March 2020)

(7) This is why we do not constantly get ill, despite viruses, bacteria

(8) Healthy humans carry viruses too!

(9) WayBack Machine: WHO Information Notice for IVD Users

(10) Understanding cycle threshold (Ct) in SARS-CoV-2 RT-PCR

(11) This Week in Virology 641: COVID-19 with Dr. Anthony Fauci

(12) This Week in Virology 640: Test often, fast turnaround with Michael Mina



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