In the last several years of high school, we’ve slowly been introduced to pieces of DNA, whether that was by doing mini interactive activities, writing various notes, or getting told to draw a diagram. However, with CRISPR-Cas9, and a website able to recreate what it does, we are able to investigate DNA in a more in-depth way, where we can look at very specific spaces, and understand their meanings. CRISPR-Cas9 is not only viewed as the current simplest and most adaptable method of genetic manipulation, but allows scientists to alter areas of a genome by removing, adding, or changing certain sections within their DNA sequence.

CRISPR-Cas9 is an effective gene-editing technology that has enhanced biomedical research. With this technology, we can fix errors in the genome, and mediate the on and off switch of genes in cells. It is a quick, easy, and cheap way of doing so as well. It is proven effective in repairing defective DNA in mice, which in turn cured their genetic disorders, and it is said that our human embryos can probably be modified as well.

This technology has two main components: gRNA (to match its intended target) and Cas9 (also known as the 9th CRISPR-associated protein) which is an endonuclease that causes DNA’s double helix to break to give changes to the genome. The guide RNA can target a specific place within the genome.

For CRISPR-Cas9 to target a specific gene, the target genome needs to be decided and identified. After, the gRNA is altered to be conscious of a certain set of AS, TS, Gs, and Cs within the DNA. Following that, the gRNA associates with the Cas 9, which is then shown to the intended cells. If this occurs near PAM, the target sequence can be just about anything.

CRISPR-Cas9 binds to the target area when Cas9 recognizes and bind to PAM notification on the DNA. This is where 2 guanines follow. If the sequence of unpaired DNA does not appear to be an exact match with a 20-nuclease sequence, the Cas9 detaches and unzips into a double helix. If it is a good match, RNA pairs with the DNA sequence which gives a DNA-RNA sequence. The binding then activates Cas9 nuclease.

Once bonding occurs, Cas9’s nuclease makes certain cuts to the DNA, occurring 3 nucleotides away from the PAM. The two active sites cut and cleave both strands of the DNA’s double helix, and the double helix breaks.

There are two ways CRISPR-Cas9 can repair a gene. The first way, NHEJ, is the more frequently used method, proven to be faster, that does not use a template However, this form is error-prone, which leads to mutations. Errors are infrequent, and repeated cycles are what cause mutations, which are often at random.

The second way to repair a gene is HDR. It has fewer errors, uses a template, and is said to be accurate. Scientists can manipulate this form of repair which results in various forms of design. With this repair method, the cell repair machines are tricked, which corrects the existing mutations.

CRISPR-Cas9 is proven to be an effective way of altering genetic mutations and is seen to have a very important role in scientific research as of late. CRISPR-Cas9 can also be used as a tool to allow scientists to easily and quickly create cell models, which then are used to push research in cancer and mental illness fields.  It is also been noted as a rapid diagnostic.

In comparing the online simulator and the paper cut-out models, the paper cutouts showed the various parts of the process like tRNA, gRNA, PAM, the Cas9 protein, the donor DNA, and the nucleotides. However, because we were only creating the model, there was no additional information, like their functions, and specific details about certain areas. The simulator did a good job of identifying where the process is occurring and also explaining every step in detail. I think to enhance the modeling activity, they could add additional cutouts with the functions of the parts that can be added to the diagram for better comprehension.

I do believe that models are a helpful way to inform outside sources about certain things, as I think that they keep the reader’s attention, and don’t bombard them with information. However, with not enough information, outside sources can be ill-informed, or further confused on the subject.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4975809/

https://www.broadinstitute.org/what-broad/areas-focus/project-spotlight/questions-and-answers-about-crispr