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CRISPR-Cas9 is a breakthrough in genetic manipulation technology used to edit genomes in cells. Versatile, cheap, and quick, CRISPR-Cas9 is reshaping genetic engineering to tackle society’ s major issues.
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I magine a world where proliferating cancers plaguing humanity can be halted with a simple injection. A world where we need not debate the stance of abortion for genetic defects in the Congressional House, but rather end the problem in the lab. A world where humans can take grasp of their genome and shape it to redefine their lives and the people around them. Although a fantasy in the present, humanity has laid a bridge to this idyllic land with the development of CRISPR-Cas9, a genomic-editing technology that holds the key to this almost utopian dream.
CRISPR, or Clustered Regularly Interspaced Short Palindromic Repeats, acts as a bacteria’ s adaptive immune system to fend off bacteriophage viral DNA injections. The mechanics of CRISPR can be categorized into two sections: spacer DNA and the Cas9 Protein.
First, in this rudimentary immune system, there is a segment of DNA called spacer DNA that is“ regularly interspaced” by the“ short palindromic repeats” of DNA strands that serve to distinguish the individual spacer DNA sections. Much like how doctors issue vaccinations to allow a human’ s immune system to familiarize itself with foreign viruses, bacteria store viral DNA in spacer DNA that enables them to fend off future attacks with this prior knowledge.
Second, the CRISPR system includes CRISPR-associated genes better known as“ Cas” genes. These subunits contain the genetic information for forming Cas proteins that act as helicases to unwind DNA and nucleases to separate individual segments. Cas9 proteins in this particular scenario cooperate with the CRISPR system to copy the stored viral DNA from the spacers and form a guiding RNA, or gRNA, to probe for new invasive viral DNA. With greater scientific involvement in this biological process, scientists like Jennifer Doudna and Emmanuelle Charpentier implemented the tracrRNA-crRNA chimera system in the Cas protein to have the tracrRNA hold the CRISPR-RNA as the protein searches for the precise position to commence and terminate excision. So this tracrRNA-crRNA chimera system moves along the double helix of DNA, guiding the Cas9 protein to look for the nucleotide bases that complement the sequence of the spacer DNA. When the guide RNA finds a match to its bases, it binds to the cell’ s DNA strands and allows the Cas9 protein to begin its excision of the viral DNA. Two nucleases( enzymes that cleave nucleic acids) on the protein cut the DNA strands in two separate pieces. At this point, the cell realizes its DNA has been damaged and begins to repair it, replacing it with DNA to fill the gap.
Two ways humans can manipulate CRISPR-Cas9 is through removal of DNA strands or introduction of new DNA, or essentially genes. For instance, if scientists would like to remove a genetic disease from a DNA strand, they could utilize CRISPR by introducing that genetic disease
THE BELL NUCLEUS · Jan 2016 | 17