CRISPR Gene Editing Technology
Written by: Christian H. Ross
Illustrated by: Megan Joyce

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DNA (deoxyribonucleic acid): molecular instructions that guide how all living things develop and function...more

Enzyme: a protein that changes the speed of chemical reactions.

Precise: exact or accurate.

Protein: a type of molecule found in the cells of living things, made up of special building blocks called amino acids.

RNA: an acid found in all living things that carries messages from DNA to the rest of the cell to be made into protein.

A bright blue fish, called a cosmic blue tetra, that was made to be blue using CRISPR gene editing technology

This "cosmic blue" tetra fish was genetically modified using CRISPR technology. Image by Robert Kamalov.

You open your eyes and find yourself in a strange world. Sheep wander by with bright green wool, you feed your trash to plastic-eating bacteria, and when the sun goes down, the trees glow in the dark. While this may seem like a world from a science fiction story, advances in gene editing technology may make such a place closer to reality than you might think.

What Is Gene Editing?

All of an organism’s DNA together is called its genome. The genome contains all of an organism’s genes. A single organism may have hundreds or even thousands of different genes. Each gene has specific instructions for how to make different organism traits, like fish scale color or what food a fish can digest.

Gene editing is when scientists make specific changes to the genes of an organism. Humans have been making changes to organisms’ genes for a long time. But now, a new technology called CRISPR is opening up new possibilities in the world of gene editing.


Ecoli bacteria viewed up close in a high powered microscope

CRISPR sequences are short bits of DNA found in bacteria, viruses, and fungi.

In the microscopic world, organisms are in constant conflict. Bacteria, fungi, and viruses compete and battle with one another for survival. Because of this, most bacteria, fungi, and viruses have ways to protect themselves. In studying how they do this, scientists discovered a special part of bacterial genomes that helps protect the bacteria against viruses. CRISPR sequences are these protective sections of genes. CRISPR stands for Clustered Regularly Interspaced Palindromic Repeats.

Viruses each have their own genetic “fingerprint”. When a bacterium is attacked by a virus, the bacteria CRISPR system records the genetic “fingerprint” of the virus. Later, when the bacterium is attacked by that virus again, the bacterium compares the “fingerprint” of the virus to those in its memory. If there is a match, the bacterium makes special CRISPR-associated (Cas) proteins. The proteins seek and destroy that specific virus by snipping it into pieces. Scientists have found a way to copy this “seek and snip” activity of bacteria to design new tools for gene editing.

Learn a bit more about how CRISPR works in action in our video, CRISPR Science: DNA, RNA, and Gene Editing.

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What Does CRISPR Do?

Different dog breeds being compared - a large great dane stands next to a tiny chihuahua

People have been modifying genomes for a long time. Selective breeding used to be the main way to modify a genome. Image by Ellen Levy Finch.

CRISPR is not the first tool that scientists have invented to make changes to genomes. Scientists have used radiation and other tools to manipulate genomes for over a hundred years. But those techniques did not always make precise changes. They could also be difficult and expensive to use. More recently, scientists developed more precise gene editing tools that use nucleases.

A nuclease is a special protein that recognizes a specific sequence of DNA and binds (or attaches) to it. When it binds, the nuclease cuts the DNA. Cutting the DNA lets scientists target very specific places in a genome to make changes. But those tools were difficult to use in experiments. They had to be specially designed for every change that they wanted to make to the genome. Designing new versions of those tools took a long time to make and were expensive.

An illustration of CRISPR Cas9

Special RNA is designed to find the location where CRISPR will cut DNA. This can remove a section of DNA, or open a spot for new DNA to be added. Click for more detail.

CRISPR also targets and cuts specific places of a genome. But CRISPR is different because it is faster, cheaper, and can be used for many different purposes.

CRISPR uses a two-part system, an enzyme and a guide RNA. Enzymes are proteins that cells make for specialized jobs. In this case, an enzyme can be used to cut strands of DNA. But how does it know where to cut? This is where RNA comes in. RNA is a sequence of nucleotides, similar to DNA, that can match up and bind with very specific DNA sequences. The guide RNA specifies the particular place for CRISPR to target and then the enzyme snips the DNA at that site.

The advantage of CRISPR is that scientists can easily exchange the guide RNA. A different guide RNA can target a different sequence of DNA. It is similar to how a drill has many bits (the small metal part that makes the hole) of different sizes that can be used for different kinds of jobs. This makes it faster, cheaper, and easier to design different CRISPR tools for many kinds of experiments.

Additional images via Wikimedia Commons and Pixabay. Soft-boiled egg by H. Alexander Talbot.

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Bibliographic details:

  • Article: Cutting DNA with CRISPR
  • Author(s): Christian H. Ross
  • Publisher: Arizona State University School of Life Sciences Ask A Biologist
  • Site name: ASU - Ask A Biologist
  • Date published: March 14, 2019
  • Date accessed: July 15, 2024
  • Link:

APA Style

Christian H. Ross. (2019, March 14). Cutting DNA with CRISPR. ASU - Ask A Biologist. Retrieved July 15, 2024 from

American Psychological Association. For more info, see

Chicago Manual of Style

Christian H. Ross. "Cutting DNA with CRISPR". ASU - Ask A Biologist. 14 March, 2019.

MLA 2017 Style

Christian H. Ross. "Cutting DNA with CRISPR". ASU - Ask A Biologist. 14 Mar 2019. ASU - Ask A Biologist, Web. 15 Jul 2024.

Modern Language Association, 7th Ed. For more info, see
Soft boiled egg

Many foods, like eggs, can cause allergies for certain people. With CRISPR technology, scientists can create a lot of helpful products, like hypoallergenic eggs.

Want to review your DNA basics? Visit DNA ABCs.

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