CRISPR is a genetic tool that is able to precisely target and edit genes. Using this technology we are able to eliminate mutations and other genetic disorders from a persons genes. We have been studying this process through paper and interactive 3D models.
What CRISPR-Cas9 means
CRISPR stands for Clustered Regularly Interspaced Short Palindromic Repeats which scientists have found to be a defense mechanism in bacteria to protect itself when it comes to contact with an infection. CAS-9 stands for CRISPR-associated protein 9 which is an enzyme that’s function is to cut the nucleotides in the targeted DNA strand.
The structure of CRISPR-Cas9
The structure of CRISPR-Cas 9 is broken down into 2 parts, Cas 9 and the guide RNA. The guide RNA is there to help CRISPR identify which gene it’s specifically looking for and once it finds that gene the Cas-9 cuts the gene out. These two parts work together to help achieve the overall goal of editing the unwanted gene.
How CRISPR-Cas9 targets a specific gene
When released the CRISPR Cas-9 will go along a strand of DNA and scan the strand for the PAM that’s associated with the gene they need to target. When the correct PAM is found the CRISPR molecule binds with the PAM.
How CRISPR-Cas9 binds to the target area of the specific gene
Once it recognizes the PAM it binds the guide DNA and tries to pair with the
unpaired DNA nucleotides. If the DNA nucleotides form a perfect pair with the guide RNA it complementary base pairs and the next step begins. If the guide RNA doesn’t match the DNA sequence CRISPR leaves the DNA alone and allows it to zip back up.
How CRISPR-Cas9 cleaves DNA
The target DNA and the guide RNA form a helix shape once they bind together. This binding activates the DNA’s cutting activities. The Cas-9 created cuts three nucleotides above the PAM and cleaves the DNA strands. This results in a double-stranded DNA break.
How CRISPR-Cas9 can repair DNA to “knock out” a gene
There are two types of repair mechanisms that can be used to repair DNA. The more common one is NHEJ. To repair the break Cas-9 recognizes the target sequence and cleaves it together. The repeated process of cleaving and repairing the DNA results in a mutation.
How CRISPR-Cas9 can repair a mutation in DNA
CRISPR Cas-9 works by finding a targeted DNA sequence and knocking it out to protect it from mutations or infections. When it finds the target DNA it binds to the strand and cuts it open to have better access to the affected area. From there it cuts out the unwanted part and puts it back together. This is process of cutting out specific nucleotides is useful when someone have a mutation in their DNA.
How CRISPR-Cas9 could be used to our benefit
Using this technology we can save people, plants and animals from harmful viruses and infections. An example of this is if crops were affected by an infection that resulted in lots of wasted crops we can use CRISPR Cas-9 technology to target that gene or DNA sequence that’s affected and knock it out of the DNA sequence.
In what ways did the model accurately reflect the process?
By using models we were able to gain a deeper understanding of the processes and how all the different parts work together. We also get a basic understanding of the shape of all the parts.
In what ways did the model misrepresent the process?
Though models show us how the process works it can create some misrepresentations about the topic. One misrepresentation it can create is about the size of the object. Due to CRISPR’s small size we can’t see all the parts very easily so we make bigger models. The only problem with this is that it can lead people to believe that CRISPR is really that big. Another misrepresentation it can create is about the shape. Through these models we are able to get a basic understanding of the shape but we don’t see the whole picture. Like many other biomolecules and molecules CRISPR is 3D not 2D. This can lead people to believe that the molecule is flat instead of 3D.
What changes could be made to the modelling activities to make them better represent the actual process?
I feel that one major change that will be have to made to models is making them 3D instead of 2D. This will help students and anyone else learning about these topics learn about the different shapes and parts of the object easier.
Models are commonly used to communicate scientific concepts to non-scientific audiences. Do you think this is an effective way to educate students and/or the public about science? Explain why or why not.
I feel that models are a great way to help younger students or students who are just starting a next topic get a better understanding but in the long run they aren’t that great. When a student first starts learning a new topic models are great because they help them understand what is going on and how it actually works by creating it themselves and actually getting to see it. I feel that as time goes on though they shouldn’t rely on models because they can create misconceptions about different features such as the size, shape or color of the object.
SOURCES:
- CRISPR-Cas9 Mechanism & Applications (biointeractive.org)
- https://www.annualreviews.org/content/journals/10.1146/annurev-biophys-062215-010822
- https://www.jax.org/personalized-medicine/precision-medicine-and-you/what-is-crispr