CRISPR explained in SUPER simple terms – here’s how it works.

Cas9 cutting DNA

Featured Photo Credit: the conversation CC-BY ND

CRISPR is exploding right now. You may have heard of them on TV,  reading articles, watching YouTube or even on the radio. So what exactly is it? What does it do? How does it do what it does? Here, we are going to do a thorough break down on CRISPR and explain how it works in simple terms.


CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. Wow, that was a mouthful of words that doesn’t make much sense. But don’t worry, we will explain the importance of this title.


To understand this title, we first address that CRISPR are DNA sequences. DNA sequences are made out of four DNA subunits, A, T, C, G and the subunits form two long strands paired with each other. Therefore, CRISPR the name is essentially a reference on how the subunits are arranged along the strand.


The arrangement of subunits is crucial for the function of CRISPR. In the CRISPR sequence, there are spaces called ‘spacers’ in between the ‘Interspaced Short Palindromic Repeats’. Some of these spacers will be very important for CRISPR’s function, as we will explain later on.


CRISPR by itself doesn’t do any gene editing. After all, it’s just a piece of DNA. But, when we combine CRISPR with something called endonucleases, it will unleash its full potential. One particular popular endonuclease is called Cas9, which is often paired with CRISPR. Endonucleases are enzymes that can cut DNAs. In simple terms, they do the actual ‘editing’ on the genomes of any cell or organism. Now, remember those ‘spacers’ on CRISPR we’ve talked about before? Cas9 is able to recognise the spacer and perform specific cutting on DNAs that matches what the spacer looks like. Therefore, CRISPR act as a ‘guide’ and Cas9 is the ‘tool’, combining them as a system makes next level gene editing – one with surgical precision.


Here’s a video demonstration on how CRISPR works:

Video demonstration on how CRISPR works from MIT

To the discovery of CRISPR, we will have to thank mother nature. CRISPR is originally found in bacterias as a defence mechanism against ‘bacteriophages’. Bacteriophages are viruses that inject their viral DNAs inside bacterias and therefore gaining control over them. In nature, CRISPR has spacers that are just like viral DNAs. Therefore, it guides the Cas9 enzyme to look for any intact viral DNAs inside the bacteria and disable them by cutting them in half.


Thanks to technology, we can now harness the CRISPR/Cas9 system’s power and use it to create/design all kinds of organisms. Gene editing technology is important as it can affect many different industries including health, medicine and agriculture. But, is CRISPR powerful enough to ‘design’ humans? How much impact does CRISPR really have? Read our in-depth articles to explore the limit of CRISPR, where we separate fiction from real science.