CRISPR stands for “Clustered Regularly Interspaced Short Palindromic Repeats”. CAS9 stands for “CRISPR Associated Protein 9”.
As you can probably guess, it has to do with repeats and the associated protein.
There are two principle components:
- Cas9: an enzyme that can cut the strands of DNA at a specific point
- gRNA: This is the guide RNA which directs (“guides”) the Cas9 enzyme to the part of the genome being altered.
What Does CRISPR/CAS9 Do?
CRISPR/CAS9 is a system found within bacteria and involved in the immune system defense. Bacteria use this tactic to cut up the DNA of invading pathogens that attack them.
CRISPR/CAS9 uses this natural bacterial response to do similar things in DNA. In particular, it is used to change DNA in an organism by cutting up the DNA in the same manner that bacteria use it to attack viruses.
CRISPR/CAS9 can go in and change specific areas in anything: food, animals, and even people.
The technology can alter the genome by removing, adding, or altering sections of a DNA sequence (where the four bases are concerned: adenine (A), guanine (G), cytosine (C), or thymine (T).
What Is It For?
CRISPR/CAS9 has the capabilities of aiding in biomedical research, treating genetic diseases, and altering negative genome traits. Further research will probably make this a leading tool for our species, regardless of whether that is a good or bad thing.
Currently, it is the simplest, most precise method of manipulating the genetic sequence. In addition, with further research, it is only getting more and more efficient.
Cas9 is the splicer. It is used by bacteria to destroy harmful viruses and is commonly referred to as the “scissors” within CRISPR/CAS9. CRISPR just tells Cas9 where to cut.
What happens is we find a target for our Cas9, then we guide them to the exact location to “cut” the DNA. When DNA is cut, the cell immediately attempts to repair the break using anything it can find. That’s when we put in the new gene we want to insert.
We can change a G to an A, or a T to a C. Or remove them entirely. Or add others.
How Do We Get The Gene In?
As the DNA is attempting to repair itself, we have a few options.
Some common ones include:
- Electric currents (punch holes in the cell to allow a “float”)
- Tiny needle to inject it together
- Propelling systems
- Encapsulate into something that will fuse with the cell and then release it on the inside
The DNA itself will do the rest. It will be permanently affixed into the DNA strand via the natural repair mechanism mentioned above.
This is a helpful video for visualization purposes. It makes it a lot easier to understand the intricate workings of something that appears so miniscule.
A Fast Summary
- gRNA guides Cas9 to the specific location we want to change
- Cas9 cuts the DNA
- The cell recognizes it is damaged and attempts to fix itself
- We input the change into the DNA
- The cell formally heals itself with our alteration
A huge implication of CRISPR/CAS9 is germline edits.
This is because any changes made in germline cells will be passed on from generation to generation down the line.
This means permanent changes in genetic lineages could become an inevitability.
On one bright side, germline edits are currently illegal in many countries. Most of the countries that have the capabilities to use CRISPR/CAS9 to its fullest have already banned them. (But that doesn’t mean it isn’t happening behind the curtain).
What Are We Doing?
Labs around the world are working with CRISPR/CAS9 to test out how it can be used for livestock, plants, and early genetic testing in mice. It’s even being used in human embryos (designer babies, anyone?). Additionally, it has shown potential for treating medical conditions that have a genetic component such as cancer or hepatitis B.
The human variants are strictly regulated, but it’s still uneasy. We are trying to recreate, or permanently change, the basis of what makes us individualist humans.
CRISPR will not be used in humans routinely for many years. But the possibility for dramatic change is evident, and likely to be arriving sooner than we think.
CRISPR/CAS9 has the potential for benefits, but the risks are extreme if taken too far. It can even be used to edit other harmful agents, potentially increasing the risk of bioterror significantly.
Keep your eyes on this tech going forward. It will probably be a big player in the years ahead.