Preface

 RNA interference (RNAi) is a widely used technology for gene silencing and has become a key tool in a myriad of research and lead discoveries. In recent years, the mechanism of RNAi agents has been well investigated, and the technique has been optimized for better effectiveness and safety. In the last few decades, advances in RNAi technology and the po‐ tential for leveraging RNAi for sequence-specific gene silencing have put it at the forefront for developing effective therapeutics against an array of diseases. siRNAs have been suc‐ cessfully usedin a variety of experimental settings both in vivo and in vitro, thereby permit‐ ting long-lasting silencing of genes of interest.

 Alongside this, the clustered regularly interspaced short palindromic repeats (CRISPR)-as‐ sociated Cas9/gRNA system is a fairly recent, novel, targeted, genome-editing techniquede‐ rived from the bacterial immune system. Recent advances in gene-editing research and technologies have enabled the CRISPR-Cas9 system to become a popular tool for sequencespecific gene editing to correct and modify eukaryotic systems. The technology allows tar‐ geted knock-ins and knocks-outs of any gene within the genome. DNA mutations ranging from a single base pair to large deletions in both in vitro and in vivo model systems have been accomplished, thereby revolutionizing the molecular biology world of science.

 In this book, we will focus on the mechanisms, applications, regulations (their pros and cons), and various ways in which RNAi-based methods and CRIPSR-Cas9 technology have stimulated the modulation of gene expression, thereby making them a promising therapeu‐ tic tool to treat and prevent complex diseases and disorders.

> **Aditi Singh and Mohammad W. Khan**  Independent scientists, USA

**Section 1**

**Introduction**

**Section 1** 
