CRISPR-CAS GENOME EDITING AND MOLECULAR DIAGNOSTICS: EMERGING PERSPECTIVES IN GENETICS AND BIOCHEMICAL RESEARCH

Abstract

Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and their associated (Cas) proteins have progressed from an obscure, unannotated repeat sequence first noted in Escherichia coli in 1987 to one of the most versatile toolkits in modern genetics and biochemistry. This chapter provides an expanded, detailed synthesis of CRISPR-Cas biology: its historical discovery and immunological origins — including the experimental confirmation of CRISPR as an adaptive immune system and the discovery of tracrRNA — the classification and structural biochemistry of Class 1 and Class 2 CRISPR-Cas systems (including the Cas9, Cas12, and Cas13 effector families and the crystal structure of the Cas9-sgRNA-DNA complex), the phage-derived anti-CRISPR proteins that naturally inhibit Cas activity, programmable transcriptional and epigenetic regulation (CRISPRi/CRISPRa), and the rapidly diversifying family of editing modalities encompassing nucleases, base editors, and prime editors, along with the distinct guide-RNA-independent off-target mechanism recently identified for cytosine base editors. It further examines how the same collateral-cleavage biochemistry that underlies genome editing has been independently repurposed for ultrasensitive molecular diagnostics, with particular attention to the SHERLOCK, DETECTR, and electronic CRISPR-Chip platforms and their clinical validation during the COVID-19 pandemic. Applications in functional genomics screening, agricultural biotechnology, and both ex vivo and in vivo therapeutics are reviewed alongside delivery strategies, empirical off-target detection methods, and the regulatory and ethical frameworks shaping clinical translation, including the 2018 heritable-editing controversy. Six original diagrams — spanning a historical timeline, CRISPR-Cas system classification, the Cas9 cleavage mechanism, the evolution of editing modalities, collateral-cleavage biochemistry, and the CRISPR diagnostic workflow — are provided to support conceptual understanding, alongside two comparative tables. The chapter closes with a discussion of open challenges and future research directions connecting basic CRISPR biology to applied genetic and biochemical research.