Applications of CRISPR-Cas9 Gene Editing in Modern Biology: From Genome Engineering to Precision Medicine

Clustered Regularly Interspaced Short Palindromic Repeats-associated protein 9 (CRISPR-Cas9) has emerged as one of the most transformative technologies in modern biology, providing researchers with a programmable and comparatively accessible approach for manipulating genomic DNA. Originally characterized as part of a prokaryotic adaptive immune system, the CRISPR-Cas9 pathway was converted into a genome-engineering platform capable of producing targeted DNA double-strand breaks using sequence-specific guide RNA. Since the first demonstrations of genome editing in mammalian cells, CRISPR-Cas9 has expanded into functional genomics, disease modeling, stem-cell biology, cancer research, agricultural biotechnology, microbial engineering, synthetic biology, and therapeutic development. Subsequent innovations, including catalytically impaired Cas9 systems, base editors, and prime editors, have further expanded the range of genetic modifications that can be achieved while reducing dependence on conventional double-strand-break repair. This paper reviews the major applications of CRISPR-Cas9 in modern biology, emphasizing the molecular basis of editing, experimental strategies, functional-genomic screening, animal and plant engineering, disease modeling, therapeutic applications, and emerging precision-editing technologies. Evidence from original research studies demonstrates that CRISPR-Cas9 has evolved from a gene-disruption technology into a versatile biological engineering platform. However, challenges involving off-target activity, delivery, editing efficiency, genomic integrity, immune responses, ethical considerations, and long-term safety remain important barriers to widespread application.iste natus error sit voluptatem accusantium doloremque laudantium