The term “CRISPR” has gained a lot of attention recently as a result of a debate among scientists about the possibility of genetically modifying the human germ line and the ethical implications of doing so. However, CRISPR is not just a method to edit the genomes of embryonic cells, as the public discussion might have implied; it is a powerful, efficient, and reliable tool for editing genes in any organism, and it has garnered significant attention and use among biologists for a variety of purposes. Thus, in addition to the discussion about human germ line editing, CRISPR raises or revives many other ethical issues, not all of which concern only humans, but also other species and the environment.
CRISPRs are short DNA sequences with unique spacer sequences that, along with CRISPR-associated (Cas) proteins, constitute an adaptive immune system in many bacteria and archaea against invading bacteriophages . By using short RNA molecules as a template, Cas makes highly sequence-specific cuts in DNA molecules that can be exploited to insert genes or to precisely modify the nucleotide sequence at the cut site. CRISPRs were first identified in the 1980s, but it is only during the past few years that scientists realized their potential to edit the genomes of any organism, from microorganisms to plants to human cells and, most controversially, human embryos. The CRISPR/Cas system is not a breakthrough technology in the sense that it enables genome editing; biologists have been using transcription activator-like effector nucleases (TALENs) and zinc finger nucleases (ZFNs) to edit genomes for some time. However, those technologies are expensive, technically challenging, and time-consuming, as they require protein engineering to target specific DNA sequences. CRISPR/Cas, in contrast, recognizes its target sequence via guide RNA molecules that can be cheaply and easily synthesized. A standard molecular biology laboratory can now edit genes or whole genomes of many organisms, as CRISPR/Cas does not require sophisticated knowledge or expensive equipment. […]
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