Simple Things* #8

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If you want to study a certain bit of parents’ information you often first have to make more of that parents’ information – from one or several pieces, to several tens of hundreds or hundreds of hundreds of hundreds of pieces. The information is stored on two long pieces that are sticking together.

In order to make more, the parents’ information is first made hot, to force the two sides to not be together anymore.

Then, you choose two very small parts of broken up parents’ information that fit to the ends of a piece of information that you are interested in. The two pieces stick to the two long pieces of information. This happens when it is only warm….

By adding building blocks and a special kind of tiny machine that works when it’s hot, the parents’ information grows longer from these small broken up parts. This happens when it is warmer than in the step before but not as hot as at the start.

Once a new bit of parents’ information has been made, that new piece can then be used as a form to make even more pieces, when the entire story is repeated.

Each repeat then makes two times more information than what was there in the time before. In the end, you have enough pieces of information so that they can be used for finding who did a bad thing, finding out how or why people are sick, finding out who is the mother or father of someone, and many other things.

Can you guess what we are describing?


The answer is: PCR!

The Polymerase Chain Reaction – or PCR for short – revolutionized molecular biology. For many experiments you need a lot of the DNA you want analyze. Before the invention of the PCR in the 1983, you could only analyze DNA of organisms you could easily multiply like bacteria. You would take a large amount of bacteria, isolate a lot of DNA and then continue with your experiment.

With a simple PCR, researchers could amplify a few pieces of DNA to give enough material for many experiments. Suddenly, a whole new world became easily accessible, especially in analytical experiments when traces of DNA were present and when the origin of it was to be found.

The key to the PCR is the Taq-polymerase. This enzyme, isolated from bacteria living in hot springs in the deep sea, is able to work at temperatures of 100 °C, when most other enzymes long stopped working. It performs the heavy work of building a new DNA strand matching the template strand in the third step of the PCR.

There are only few tools and developments that transformed molecular biology as much as the PCR did. That’s why its inventor, Kary Mullis, was awarded the Nobel Prize for Chemistry in 1993 along with Michael Smith.

*In which we use Randall Munroe’s ‘simple writer‘ to explain plant-and-pipette topics. Can you guess what they are?

Monroe’s ‘simple writer’ limits language use to only the 10 hundred most common words in the English language. So the word ‘chloroplast’ is out. But so is ‘duck’, ‘cuddle’, and ‘explosion’.

We’ve tried to define a plant and pipette related word using only these common words. Can you tell what we’re talking about? The solution is shown at the bottom.

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