How Does CRISPR Work?

show/hide words to know

Bind: attaching two things together.

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

Gene expression: the conversion of the information encoded in a gene into a final product. This is most often a protein....more

Molecule: a chemical structure that has two or more atoms held together by a chemical bond. Water is a molecule of two hydrogen atoms and one oxygen atom (H2O)... more

Nuclease: a type of protein that breaks nucleic acids like DNA into smaller pieces.

Nucleotide base: a building block of both DNA and RNA. Nucleotide bases are often referred to just by their first letter. There are four nucleotide bases that make up DNA: adenine (A), cytosine (C), guanine (G), and thymine (T). RNA is similar but has the nucleotide uracil (U) instead of thymine (T)....more

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.

CRISPR: One Tool, Many Uses

Swiss army knife with several of the tools unfolded.

CRISPR can be thought of as a biological Swiss Army Knife, with many ways to complete different jobs. Image by Jonas Bergsten.

What’s better than a tool that is good for one job? A tool that is good for lots of different jobs! CRISPR is like a biological Swiss Army knife. It can be used as a tool to do many different kinds of tasks in all kinds of organisms, from bacteria to humans.

Before CRISPR, many scientists still manipulated DNA in their experiments to better understand how living systems work, but they used other tools. Scientists used to use nuclease tools or special chemicals to make changes to DNA. But now, those scientists can do their same experimental research, but with CRISPR. This makes CRISPR useful for many different kinds of research. For example, CRISPR is used in research in genetics, animal behavior, evolution and development, and personalized medicine. CRISPR is especially useful in synthetic biology and bioengineering research.

K.O.! Gene Knockouts

A brown, brindled mouse next to a dark brown lab mouse. The light brown mouse had certain genes associated with hair growth knocked out.

The lighter mouse, on the left, has been genetically modified to knockout a gene affecting hair growth. Click to enlarge.

The most common use of CRISPR as a research tool is for performing gene knockouts. Gene knockouts are when scientists make genetic changes to permanently make a gene no longer function. For a gene knockout, scientists can target a specific site in a gene of interest for CRISPR to cut. When that cut is made, the cell’s natural DNA repair processes try to fix the damage to the gene. But sometimes these repair processes make mistakes by inserting or deleting additional nucleotide bases at the cut site. These mistakes often stop the gene from functioning normally. By studying the effects of knocking out a certain gene, scientists can learn more about that gene’s function.

Shhh! Gene Silencing

Scientists also use CRISPR for things besides making changes to DNA. They also use CRISPR for gene silencing. Gene silencing is when the introduction of a molecule blocks the function of a gene. Unlike a gene knockout, gene silencing only temporarily affects gene function.

DNA illustration with DNA in blue and background in black

Gene silencing can be used to stop certain genes from being expressed, without changing the underlying DNA. Image by PublicDomainPictures from Pixabay.

New tools have also been developed, just for gene silencing. Scientists have made a new class of CRISPR-associated proteins, called dCas proteins. dCas proteins are exactly like other CRISPR proteins except that they do not cut the DNA. Instead of cutting DNA, the dCas proteins only bind to a target location. As long as they are bound to the DNA, the dCas proteins stop gene expression at that location of the genome. Scientists can learn about the function of genes by observing the changes before and after gene silencing from the introduction of dCas proteins.

CRISPR makes gene editing precise, cheap, and easy to do. Because of this, CRISPR has been adopted in science laboratories across the world as a basic research tool.

Albino Anolis lizard image from Ashley Rasys et al "CRISPR-Cas9 Gene Editing in LizardsThrough Microinjection of Unfertilized Oocytes," published under CC-BY-NC 4.0 International licence by bioRxiv.

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Bibliographic details:

  • Article: CRISPR in Research
  • 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: June 16, 2021
  • Link:

APA Style

Christian H. Ross. (2019, March 14). CRISPR in Research. ASU - Ask A Biologist. Retrieved June 16, 2021 from

American Psychological Association. For more info, see

Chicago Manual of Style

Christian H. Ross. "CRISPR in Research". ASU - Ask A Biologist. 14 March, 2019.

MLA 2017 Style

Christian H. Ross. "CRISPR in Research". ASU - Ask A Biologist. 14 Mar 2019. ASU - Ask A Biologist, Web. 16 Jun 2021.

Modern Language Association, 7th Ed. For more info, see
Albino and wild type Anolis lizards
In April 2019, researchers at the University of Georgia announced they had made the first gene-edited lizards using CRISPR Cas9. Here, the albino Anolis lizard on the left was one of four albino lizards that hatched from eggs that were genetically modified while still in the mother lizard.

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