May 14

What is Polymerase Chain Reaction? | PCR Explained

2 Minute Classroom writes “Thanks for stopping by, this is 2 Minute Classroom and today we are talking about Polymerase Chain Reaction, or PCR as it’s more commonly known. First, let’s talk about what PCR is and how it works, and then I’ll give some examples of what PCR is used for.

PCR is a technique used to amplify or copy small specific segments of DNA.

For PCR to be successful, you need the DNA sample you want copied, DNA primers to identify the specific sequence of DNA you want to amplify, lots of raw nucleotides to form the DNA copies, and a heat resistant DNA polymerase to make the new copies. This all goes into a special stable solution.

Once all the ingredients are in, you run the solution through many temperature cycles until you reach the amount of DNA copies needed.

There are three main steps to this cycle.

Step 1 – Denaturation

The solution is heated allowing complementary DNA strands to separate so that all the DNA in solution is single stranded.

Step 2 – Annealing

The solution is cooled so that the DNA primers can bind to the specific region of DNA you are interested in.

Step 3 – Extension

The temperature is raised so that the DNA polymerase can bind and perform the necessary operation of synthesizing new DNA strands.

This cycle is repeated about 30 times, takes about 3 hours and creates over one billion copies.

So what is PCR actually used for?

PCR has many research based and practical applications.

It’s used for DNA mapping, like the Human Genome Project.

It’s used to check sections of DNA for genetic testing to determine potential disorders.

Companies like 23andMe and use PCR for to run personal DNA tests.
And my favorite application for PCR is in forensics. Whenever a crime is committed, the perpetrator almost always leaves their DNA at the crime scene. This could be hair, semen, skin, or blood. Investigators search for this evidence and thanks to PCR, can amplify the DNA and compare it to the DNA of suspects. This genetic information is then put into the FBIs DNA databade, CODIS

But it gets even better. Investigators have been able to take DNA evidence from crimes committed before CODIS was put together and run it through the current system. This has solved many cold cases and also exonerated prisoners who had been wrongfully accused, even some that were on death row.

Needless to say, PCR is one the most important scientific advances ever. And now you know why.”

2 Responses to “What is Polymerase Chain Reaction? | PCR Explained”

  1. Wolf

    And what should it NOT be used for? … testing for viruses as it inevitably leads to large numbers of false positives
    Yet the wrold is going through waves of lockdowns and loss of rights because of this method of testing… cui bono?

  2. richard r

    Intersting side story is the inventor of the “polymerase Chain Reaction.” (Kary Mullis) who won a nobel prize for it also told a strange story about seeing a glowing racoon that spoke to him once in a book he wrote.,”Dancing Naked in the Mind Field” , he swears it was true. .he took lsd too, hehe.

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