CRISPR was discovered by scientists trying to understand how bacteria and viruses interact. They found that CRISPR acts like scissors, cutting DNA to defend bacteria. In the 2010s, scientists realized that DNA scissors would make a great tool for editing DNA! They figured out how to make CRISPR proteins cut DNA at almost any place they wanted. 

When a cell’s own DNA is damaged, the cell repairs it. This repair process is when changes can be made. When DNA is broken, sometimes the cell glues the two ends back together. This doesn’t always work perfectly, and sometimes DNA letters get deleted or added, which can make the gene stop working. So, CRISPR can be used to turn genes “off” by making a cut that is repaired in this sloppy way.

Scientists can also give the cell a piece of repair DNA. The repair DNA is a sequence that the scientists want to add at the location of the CRISPR cut. The cell will copy this sequence over the break, sort of like putting a patch over a hole. Using this trick, scientists can add new sequences or whole new genes into an organism. 

Using CRISPR tools to change DNA is called CRISPR-based gene editing — but for short, people usually just call it “CRISPR.” Labs all around the world use CRISPR to edit DNA. And scientists are working on making new and better CRISPR tools all the time. 

Scientists usually do basic or applied research. Basic research answers questions about how the world and living organisms work. Applied research uses that knowledge to solve problems. Applied research often involves making medicines, machines, and tools.

Scientist use CRISPR in their research in a few main ways:

• Figuring out what genes do
• Studying human, animal, and plant diseases
• Creating medicines or treatments

Scientist can use CRISPR to figure out what a gene does.

You can think of an organism as a complicated machine with lots of parts. Each gene is one part. To learn what a gene does, you can turn it on or off and see what happens. Scientists can use CRISPR to turn genes on and off.

How do you figure out what each part of a complex system does?

Another way to learn more about genes and organisms is to copy a gene from one organism and paste that gene into another organism. For example, green iguanas have spikes going down their back, but dragon lizards don’t have any spikes at all! Maybe the answer is in their genes. Scientists can try adding a gene or a group of genes from the green iguana’s DNA to the dragon lizard. If the dragon lizard grows spikes, that means you’ve found the DNA that make spikes grow! 

Researchers can use CRISPR to study all kinds of organisms. Right now, researchers are using CRISPR to understand things like: 

• How tomatoes control when they flower and ripen
• How butterfly wings get their special patterns
• How squids can change colors to blend in with their environment

Gene variants are changes in some of the DNA letters of a gene. For instance, every butterfly has genes that make them grow wings! But gene variants — a few changes in the DNA letters — make those wings big or small, spotted or striped. Humans have variants in genes, too, that can affect almost any trait.    

Many variants contribute to the differences we notice on our friends and families, like how tall people are, if they have big or small feet, and whether or not they have freckles. Some variants can also cause diseases, and others can help prevent diseases.

Many scientists are motivated to figure out what causes diseases so eventually treatments can be made. Making a disease treatment takes a lot of basic research! Scientists need to figure out things like: 

• Is the disease caused by a gene variant? 
• Are there gene variants that protect people from this disease? 
• What happens in someone’s body when they are sick?

CRISPR makes it easier to make genetic changes to cells or animals. This makes it possible to figure out if a gene variant causes a disease. CRISPR also makes it much easier to figure out if gene variants protect against a disease. Can you think of how a scientist might do this? 

To answer questions about diseases, scientists need to do experiments. But, they can’t just do experiments on living human patients. So, scientists create disease models. A disease model could be cells in a petri dish. It could also be a whole organism, like a banana plant or a mouse. The cells or organism are made to have some features of the disease.

Creating disease models used to be hard. But CRISPR makes it easier to change DNA. Scientists can use CRISPR to add or remove gene variants in order to create models, better understand diseases, and develop treatments. With CRISPR, scientists can: 

• Turn a gene on
• Turn a gene off
• See how having different variants of a gene affects a plant or an animal 
• Put a gene variant that might cause a human disease into an animal disease model and see what happens
• Combine a gene variant that might be protective AND one that is harmful and see what happens 

You'll learn more about using CRISPR in medicine and farming in the next sections! 

CRISPR can be used to edit genes, turning them "on" or "off," and swapping gene variants. There are two main types of research: basic research, to figure out how the natural world works, and applied research, to make things like machines or medicines. CRISPR can be used in basic or applied research. Scientists use CRISPR in basic research to learn what different genes and gene variants do, create disease models, and study the genetics of diseases.

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