A Comprehensive Review on CRISPR-Based Screening and Its Applications

CRISPR-based tools have quickly moved from specialist techniques to routine instruments in biology and medicine, and they are now central to large-scale loss-of-function and perturbation screens. In this review, we focus on how pooled CRISPR screens are used to interrogate gene function in living cells, most often through cell fitness or simple selectable markers, and contrast this with arrayed formats that trade throughput for richer molecular readouts, such as transcriptome-wide changes. We bring together current strategies for library design, delivery, and selection and show how different Cas nucleases, including Cas9, Cas12, and Cas13, broaden the range of genome and transcriptome perturbations that can be assayed. We then discuss recent applications in drug response, viral infection, and cancer biology and consider how improvements in high-content technologies, data analysis, and emerging diagnostic uses are likely to shape the next generation of CRISPR-based screening studies.