As the field of biotechnology grows, chemists and biologists face an ever-increasing conundrum of ethical hurdles caused by technological breakthroughs. Genetic engineering is on the cusp of a revolution. Breakthroughs in genetic engineering (GE) technologies will soon make modifying the DNA of living organisms easier, cheaper and more efficient than ever before. GE technology is used to modify the DNA of living organisms and has many different applications. One of the most promising applications of GE technologies is gene therapy. Gene therapy is a technique by which biologists modify the DNA of living subjects with the aim of curing genetic diseases (Gura, 2001). Early controversies over the use of gene therapy to treat disease were galvanized by the death of a hemophilia patient during a gene therapy trial (Gura, 2001). The biggest obstacle facing any emerging GE technology is uncertainty about the risks associated with it. Today's leading GE technology, CRISPR/Cas9, is no exception to this rule. Although CRISPR/Cas9 is poised to revolutionize the world of genetic engineering, there is considerable opposition from the general scientific community to its use and the potential side effects that could arise from unknowingly using it (Gilles and Averof, 2014). . A brief overview of DNA/RNA technology, as well as CRISPR/Cas9 technology, coupled with an analysis of the potential disadvantages and advantages of CRISPR/Cas9 will allow the reader to better understand the dynamics of the controversy and reach their own consensus on the subject. .Say no to plagiarism. Get a tailor-made essay on “Why Violent Video Games Should Not Be Banned”? Get an original essay To understand the mechanism of CRISPR/Cas9, one must be familiar with the function and process of DNA and RNA in the cell. DNA, deoxyribonucleic acid, is the cornerstone of all life. It is made up of two complementary nucleotide chains. Each nucleotide is made up of a phosphate group (PO4), a deoxyribose sugar arranged in a 5C ring (C5H10O4) and a nitrogen base (Adenine, Guanine, Thymine, Cytosine). Nucleotides are covalently linked to each other by a phosphodiester bond formed between the 5C sugar of one nucleotide and the phosphate group of another nucleotide. The two strands of nucleotides are linked by hydrogen bonds formed between complementary nitrogen bases. Adenine has complementarity with thymine, while guanine has complementarity with cytosine (Thieman & Palladino, 2013). The two strands of nucleotides form a double-stranded, double-helical structure called DNA. DNA is essential for cellular function because it codes for all proteins found in a cell. In order to produce a protein, DNA must first be copied by another nucleic acid, RNA. The RNA then sends a copy of the DNA to the cell's ribosomes which translates the RNA sequence into a string of amino acids to form a protein (Thieman & Palladino, 2013). The entire process of transcription and translation is beyond the scope of this article, so it is enough to understand the fundamental underlying function of DNA as the "code" for life, and RNA as a translator of DNA. DNA sequences are “read” as letters indicating nitrogen bases in the direction 5-prime (5') to 3-prime (3'). 5' refers to the end of the sequence with a phosphate group attached to the fifth carbon of the deoxyribose sugar. For example, a sequence of adenine-thymine-guanine-cytosine would read as ATGC. AA particular sequence of DNA with a known function is called a gene. The location of a gene is called its locus. Clustered regularly interspaced short palindromic repeats, or CRISPR, derive from a natural immune response of bacteria to viral infection (Gilles and Averof, 2014). CRISPR refers to one or more loci found in the genome of bacterial cells. The mechanism of CRISPR involves the incorporation of viral DNA into the CRISPR sequence in order to allow the bacteria to produce an RNA strand complementary to the viral DNA. This is called “CRISPR-derived RNA (Gilles & Averof, 2014)” or crRNA. The crRNA binds to “CRISPR-associated proteins (Cas) to form an active CRISPR/Cas endonuclease complex (Gilles and Averof, 2014). » An endonuclease is a protein that has the ability to degrade DNA. CRISPR/Cas9 refers to a specific endonuclease produced by the bacteria Streptococcus pyogenes. CRISPR/Cas9 contains two forms of RNA and the Cas9 protein. The crRNA contains the sequence necessary to bind complementary to the viral DNA. Another type of RNA, “trans-acting antisense RNA, also known as tracRNA,” contains the sequence necessary to “form a complex with Cas9 (Gilles & Averof, 2014).” Together, crRNA and tracRNA form the “guide RNA” of the complex. The last element, Cas9, is a protein that acts as the nuclease of the complex. The mechanism of CRISPR/Cas9 requires that a short sequence of nucleotides following the sequence targeted by the guide RNA (gRNA) be present in the target DNA. This sequence, called “protospacer adjacent motif” (PAM), is necessary for the functioning of Cas9 (Gilles & Averof, 2014). The CRISPR/Cas9 complex has been modified by scientists to contain any desired gRNA sequence, allowing targeting. of any PAM-containing gene. In bacteria, the CRISPR process ends with the uniform cleavage of DNA occurring a few nucleotides upstream of the PAM. For bacteria, this is an effective method of destroying viral DNA. In eukaryotes, however, CRISPR/Cas9 is used to target a gene and insert, delete, or modify that gene. The exploited CRISPR/Cas9 complexes exploit two types of repair mechanisms used by DNA (Gilles & Averof, 2014). The first process of non-homologous end joining or NHEJ does not require a homologous strand (DNA containing the same genes with potentially different alleles) of DNA for repair. In NHEJ, the cut ends of the DNA are simply brought back together and the bonds are reformed. NHEJ can result in the deletion of DNA sequences or introduce (insert) new DNA into the strand during repair (Reis, Hornblower & Tzertzinis, 2014). The other repair mechanism, homology-directed repair or HDR, requires a homologous DNA strand to copy a short section of DNA used to repair the broken strand. HDR can be exploited by introducing homologous DNA containing a mutated or normal form of the gene being repaired. Deletion of a gene is called knockout and is usually done via NHEJ, and insertion of a gene is called "knock-in" and can be done by NHEJ or HDR (Reis, Hornblower & Tzertzinis, 2014) .CRISPR/Cas9 confers a number of advantages over other gene editing technologies. First, CRISPR/Cas9 is much simpler than previously implemented gene editing technologies. Two other technologies that work on a similar principle to CRISPR/Cas9, zinc finger nucleases and TALENs (Transcription activator-like effector nucleases), are much more technically challenging. Another advantage offered by CRISPR/Cas9 is specificity, as long as the targeted gene has the correct protospacer adjacent motif, then CRISPR/Cas9..