CRISPR- Cas9 Assingment

In class, we have been investigating a gene-editing technology called CRISPR-Cas9. Gene-editing technologies like CRISPR- Cas9 allow genetic alterations to a cell’s genome by editing sections of the DNA sequence (removing, adding, and altering). The CRISPR-Cas9 method stands out for its efficient, precise, and fast-working qualities. We have been exploring CRSPIR-Cas9 through a physical simulation using paper cut-outs along with online simulations to develop a better understanding how it operates.

CRISPR-Cas9:

CRISPR- Cas9 is a biotool that is used for genetic alterations. CRISPR is short for “Clustered Regularly Interspaced Short Palindromic Repeats”. More specifically, it is repetitive, partially palindromic, DNA sequences found in the genome of bacteria. Meanwhile, Cas9 is an enzyme that stands for “CRISPR-associated protein 9”. Its function is to cut DNA at specific locations, which can be programmed by scientists.

 

CRISPR is comprised of repeating sequences in the DNA genome of bacteria. CRISPR has two main components which include a Cas9 protein and synthesized a gRNA or guide RNA. The CRISPR nuclease targets on selected genes. The gRNA’s purpose is to lead the Cas9 protein to the intended gene for editing and is meant to be complementary to the taget DNA sequence. To target a specific gene, a trinucleotide sequence called PAM (protospacer adjacent motif) is also required for recognition. This nucleotide is primairily used to pinpoint target sites. Cas9 bonds to the PAM sequence and it unwinds the double helix. Using complimentary base pairing, the gRNA will bond to the nucleotides on the DNA strand as long as they match perfectly. 

To cleave DNA, the Cas9 nuclease activates as it will be bonded to its target RNA. The Cas9 nuclease will then make precise cuts to both stands on the DNA double helix. This is done by utilizing the two active sites on its nuclease domain. CRISPR-Cas9 can repair DNA through a method called Non-Homologous End Joining (NHEJ). The Cas9 molecule will be sent into a continuous sequence of cleavage and repair due to the correctly mended breaks. Eventually, a mutatuon will occur within the targeted gene and it will be ‘knocked out’ if it occurs within its coding region. Another method used to repair a mutation in DNA is called Homology-Directed Repair (HDR). A DNA template is used to repair the caused DNA double- stand breakage through homologous recombination. After breaking the double strand, the cell is meant to use the DNA template to repair the break. If executed correctly, the targeted DNA sequence is swapped out properly thus, repairing the mutation. 

 CRISPR- Cas9 has distinguished advantages that can be applied to better healthcare and even agriculture. Currently, it is recognized as a new type of antiviral therapy that could combat numerous incurable infections (HPV, infections that lead to cancer, etc.). In the future, it could potentially serve as a cure to chronic infections, eye diseases, protein folding disorders, cancer, and blood disorders. If not a cure, it aids especially in cancer research. Outside of the medical field, it could be used within the agricutlural field. CRISPR-Cas9 could one day effectively be used to make food with an improved shelf life and resistance to pests.

The CRISPR modelling activity using paper cut-outs that we completed in class was mainly accurate in redlecting how it operates. It demonstrated the targeting, binding, cleaving, and DNA repairing methods efficiently and interactively. It also clearly distinguished the different steps of the process and aid in a good 2D visual. However, the model faultered in represerning the unwinding of the two DNA strands. I would somehow make this an addition to this activity as it would create a more seamless learning experience. The digital simulation was a great addition to the paper simulation as it included a 3D, labeled, and deteialed process of CRISPR-Cas9. I found it exceptionally helpful for accurately identifying the different components and steps. Models are effective ways to educate students and especially those who are visual learners. After viewing a model or process, it is easier to apply the knowledge and terms in your head to a visual. It also aids in explaining the process as you can better describe what is happening and picture it in your mind.

 

Works Cited

A Breakthrough Technology, Biointeractive, 11 Apr. 2018, https://youtu.be/cxhPb_BxiMc?si=akLG8THPjLRx3B1v. Accessed 20 Oct. 2023.