BIOTECHNOLOGY - CRISPR CAS9.docx - Assignment 4 –...

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Assignment 4 – BiotechnologyCRISPR – Cas 9Genes define every single living thing on earth, that includes the tiniest single-celled organism and also the biggest creatures walking on the surface of the earth today. Inrecent advancements in gene editing tools, scientists can change an organism’s fundamentalfeatures almost indefinitely. For instance, manipulating the genes of crops to be resistant todrought, mass-producing bigger fruits, and maybe even coming up with cures for geneticdiseases. This is where CRSPR comes in. CRSPR can be considered the fastest, easiest, andcheapest of the gene editing tools responsible for this new wave of science (Henle A.M.,2019). Clustered Regularly Interspaced Short Palindromic Repeats, or CRISPR, andCRISPR-associated protein-9 nuclease (Cas 9) genes are both vital in the adaptive immunesystem of archaea and bacteria to defend against invading viruses (Reis, Hornblower, Robb &Tzertzinis, 2014). Hence, it can be considered as natural process. CRISPR uses Cas 9 proteinto recognize the viral DNA and swiftly destroys it (Heler et al, 2015; Jinek et al, 2012).Although CRSPR has the potential to execute extraordinary functions which excites themedical field, the side-effects of gene manipulation seem to be unknown and has beencriticized for being unethical. There are actually several alternate approaches to targetgenome modification, but they cost a lot, time-consuming, and inefficient. CRISPR Cas 9 hasproven otherwise (Reis, Hornblower, Robb & Tzertzinis, 2014). This paper will elaborate thestages of CRISPR-Cas 9 defence and how it affects the genome engineering field.Through CRISPR RNA (crRNA), it facilitated the discovery of CRISPR system inbacteria and archaea as an acquired adaptive immune system that fight against viral DNAbased on DNA recognition and Cas nucleases-mediated DNA cleavage (Jinek et al, 2012).Any foreign DNA penetrating into the bacteria can be recognized slotted into a genome locus.That genome locus creates a CRISPR region. Protospacer is a terminology used to describethe slotted foreign DNA (Ma, Zhang & Huang, 2014). The CRISPR locus also contains of aseries of conserved repeated sequences interspaced by distinct non-repetitive sequence namedspacers. The spacers are sort out by Cas nuclease into small DNA fragment (Zhang, Wen, &Guo, 2014). As the viral DNA invades the genome of the host bacteria or archaea, the spacersare utilized as transcriptional templates, which produces crRNA. CRISPR RNA (crRNA)binds with Cas protein to make accurate breaks on target DNA sequences of the viruses. TheCRISPR-Cas system works in approximately 40% genomes of bacteria and 90% genomes ofarchaea (Grissa, Vergnaud & Pourcel, 2007). There are forty various kinds of Cas protein
families that have been discovered. These families play crucial roles in crRNA biogenesis,spacers incorporation and invading DNA cleavage. Hence, Cas proteins can be classifiedbased on the structure and sequence (Haft, Selengut, Mongodin & Nelson, 2005).

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