How does CRISPR-Cas9 gene editing work?
CRISPR-Cas9 is essentially a pair of molecular scissors guided by a GPS. The system has two components: the Cas9 protein, which cuts DNA, and a guide RNA that directs Cas9 to a specific sequence. In nature, bacteria use this to defend against viruses by storing snippets of viral DNA in their CRISPR arrays. We repurposed this by designing a single guide RNA that matches a target gene. When introduced into a cell, Cas9 binds to the guide RNA, scans the genome, and makes a precise double-strand break at the target site. The cell's own repair machinery then kicks in—either by non-homologous end joining, which disrupts the gene, or by homology-directed repair, which can insert a new sequence. It's a powerful tool, but with great power comes great responsibility.
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