How Are We Able to Edit Genes Using CRISPR-Cas9 Systems?

CRISPR-Cas9 systems stands for: clustered regularly interspaced short palindromic repeat-Cas9 systems. It is a technique used for gene editing. The researchers who developed CRISPER-Cas9 systems were inspired by the defense mechanisms bacteria use against viruses. 

Unlike bacteria, viruses cannot reproduce nor carry out metabolic activity by themselves. This is why viruses need a host, such as a bacterial cell, to exist for generations to come. After latching on, the DNA viruses inject into bacteria essentially reprograms the bacterial cell to produce viruses. But that’s not the only part. The impregnated bacterial cell eventually explodes, releasing a hoard of baby viruses. 

As a result of evolution, CRISPR-Cas systems are commonly found in bacteria, since the bacteria with immunity systems that managed to resist virus impregnation raids lived to produce offspring. CRISPR-Cas systems consist of CRISPR, repetitive DNA sequences, and Cas proteins. DNA cutting proteins patrol bacterial cells, and if virus DNA is found, it is snipped and added to the collection of viral DNA in CRISPR. The Cas proteins are like scissors that use CRISPR as a reference to quickly identify and cut virus DNA. 

The Cas proteins planted an idea into researchers’ minds. They could inject Cas proteins, along with a template RNA sequence to lead Cas proteins to a DNA sequence. Then, the Cas proteins could modify this segment of DNA by cutting it with surgical-like precision. This idea gave way to the birth of the gene editing technique: CRISPR-Cas9. 

As of now, CRISPR-Cas9 has been used to genetically modify plants. Unlike in the past, when humans selectively bred plants to create a plant with desired traits, CRISPR significantly shortens this process. CRISPR-Cas9 has been used to produce rice that is more resistant to demanding climates, bananas that are more resilient against fungus attacks, and heirloom tomatoes that are more rich in flavor. In fact, it is not out of the question that you have already eaten food genetically modified by CRISPR-Cas9. 

CRISPR-Cas9 has also been used to treat sickle cell disease and genetic forms of blindness. However, genetically modifying human somatic cells are a completely different story from genetically modifying human embryos, which could result in the genetic modifications passing on for generations. While CRISPR-Cas9 unlocks wonderful possibilities, bioethicists continue to look at this tool through a critical lens.

Works Cited

Ishino, Yoshizumi, et al. “History of CRISPR-Cas from Encounter with a Mysterious Repeated Sequence to Genome Editing Technology.” Journal of Bacteriology, American Society for Microbiology, 12 Mar. 2018,

Molteni, Megan. “How Does Crispr Gene Editing Work?” Wired, Conde Nast, 26 Apr. 2018,

Niiler, Eric. “Why Gene Editing Is the Next Food Revolution.” How Crispr Could Transform Our Food Supply, 29 Aug. 2018,

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