CRISPR: Clustered Regularly Interspaced Short Palindromic Repeats

CRISPR

Did you know that CRISPR sequences were first discovered in 1987? If you are curious about what exactly this term means, you’re in the right place. We have put together this guide to share everything there is to know about CRISPR.

Read on to learn all the ins and outs.

What Is CRISPR?

The acronym CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats. CRISPR itself is a tool that is used to edit genomes. Researchers have the ability to use this tool and alter a DNA sequence to help modify the functions of a gene.

CRISPR refers to repetitive DNA sequences that scientists observed in bacteria with some spaces in the sequences in between the repeats that match viral sequences.

Scientists came to the realization that bacteria transcribe the DNA elements into RNA when there is a viral infection. Then the RNA guides a protein called a nuclease to the viral DNA in order to cut it and provide protection against the virus.

What Are the Implications?

It is fairly easy to disrupt the targeted gene with CRISPR. The entire process has changed biomedical research in many ways. One of the main reasons it has had the ability to change biomedical research is by reducing the expense and the time involved with developing animal models with certain genomic changes.

Many scientists have been using the CRISPR system in mice to learn more about how this tool can help. Also, researchers have been trying to learn more about helping human diseases that deal with known mutations. For example, diseases like cystic fibrosis.

A disease such as cystic fibrosis can have DNA inserted into it to help correct the mutation in theory. As of the writing of this post, there are some trials going on for the clinical application of engineering T cells outside the body for an inherited form of blindness and for cancer therapy.

Another application where we see CRISPR in action is with the Kenneth Chien Moderna. With this technology according to Dr. Chien, other diseases in the liver can benefit from it.

How Does It Work?

The CRISPR tool is made up of two key molecules that help introduce a mutation or a change into the DNA. One of the molecules is a piece of RNA that is made up of a small piece of pre-designed RNA sequence. This pre-designed sequence is around 20 bases long and it is located in a longer RNA scaffold.

Then this scaffold binds to the pre-designed sequence and DNA and guides this to the right part of the genome. This allows the enzyme to cut at the perfect point in the genome.

The second molecule is an enzyme that is called Cas9. Cas9 acts like a pair of molecular scissors where it has the ability to cut the DNA strands in a specific location in the genome. This is where parts of DNA can be either removed or added.

What Are the Limitations?

Although this is a powerful tool, there are a few limitations as well. For example, this tool is not always 100% efficient which means that even the cells that take in CRISPR might not have genome editing activity.

Another limitation is that it is difficult to deliver CRISPR material to mature cells in large quantities. This limitation means that when it comes to clinical applications not having large numbers delivered is a problem.

Also, CRISPR tools are not 100% accurate yet, so this means that there can be severe consequences, mainly in clinical applications.

Ethical Issues

The applications of CRISPR technology have raised many ethical questions because it involves tampering with genomes. Unfortunately some people have taken CRISPR technology and used it for unethical purposes such as experimenting in human embryos.

Also, making any genetic modifications to reproductive cells like eggs or sperm is another ethical issue because this is considered misuse of this tool.

Future of CRISPR

It more than likely won’t be a while until CRISPR-Cas9 is routinely used in humans to make changes in a DNA sequence. There is a lot more research that has to be done on animal models and on isolated human cells in order to reach a point where CRISPR can be used to treat diseases in a human body.

Researchers are also performing a lot of work to help remove the “off-target” effects. These effects are when the CRISPR-Cas9 system cuts at a random gene instead of the gene that was intended to be edited.

Scientists are working hard to find a way for CRISPR tools to bind accurately and also cut accurately. One way that they are seeing to improve this is via the use of a Cas9 enzyme that will only cut a single strand of the target DNA instead of the double strand of DNA.

What this means is that the 2 guide RNAs and the two Cas9 enzymes will have to be in the same place in order for the cut to be made correctly. This will help reduce the probability of the cut being made in the wrong place.

Another way is to design better and more specific guide RNAs. This can be done with the knowledge of the DNA sequences of the genome along with the off target behavior of different Cas9 versions.

Feeling Like a CRISPR Pro?

Hopefully we have cleared up everything there is to know about CRISPR. As you can see there is a lot to learn about this science and research.

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