Before targeedt genome engineering emerged there was classical plant breeding and transgenic methods to modify crop plants, and ensure sustainable production. Researchers today have utilized methods like zinc finger nucleases (ZNF) and TAL effector nucleases (TALENs) to create these improved crop plants. Recently, a new method has caught the eye of many researchers; a method that simplifies the process and saves labor: CRISPR-Cas9 system.
This method of genome engineering is particularly interesting not only for researchers but also for millions of Americans. In the last decade, there has been a surge of legislation concerning GMOs. Specifically, allowing labels to be placed on genetically engineered food (crop plants) so that consumers can be aware of what they are buying or to allow for easier identification of genetically engineered food. However, the CRISPR method introduces modifications in the genome that are indistinguishable from non-GMO crop varieties, excluding these crop plants from the GMO legislation.
Most crop plants are genetically modified for improved yield. This is done so that crop plants are less prone to disease, pesticides, or insects. An example of this is Bt corn. As discussed in Dr. Postlethwait’s lecture, an organism like a crop plant could have a segment of DNA (specifically an exon) that when transcribed could code for a protein that is harmful or disruptive to the life of the plant. By cutting out the maladaptive exon and repairing the strand the plant’s DNA is genetically altered. The repair can either excise the gene and join the existing DNA molecules or incorporate a wanted DNA sequence into the genome thusallowing the DNA segment to either code protein for a newly introduced gene or no longer code that segment entirely.
With advancement of technologies for genetic modification like the CRISPR-Cas9 systems, researchers can have alternatives to the cumbersome methods of ZNF and TALENs. For example, the way in which ZNF interact with each other and DNA is quietquite complicated; each ZF must be paired with three nucleotides in the DNA. If they are not paired correctly the ZNF does not bind very well with the DNA. The high specificity of the ZNF can be challenging to make. In summary, the ZNF would require two different DNA binding proteins flanking a sequence of interest with each having a C terminal FokI nucleus module (Belhaj, 2013). However, the CRISPR-Cas9 method offers a less complicated and less laborious method design with easier programmability, flexibility and versatility for genetic modification.
Specifically, the components that comprise this method are less than those of the ZNF method. In a study by Jinek et al, the researchers were able to lower the number of components for the CRISPR-Cas9 system to two components by utilizing the Cas9 and sgRNA. The Cas9 component of the system is a protein that contains two nuclease domains that are able to cleave the complementary and non-complementary DNA...