RNA inference is new concept in gene therapy it acts by expression of specific genes to treat various diseases like cancer. It is also called as RNAi. In presence of dicer enzyme long double stranded RNA (dsRNA) is cut to small interfering RNAs called SiRNAs. SiRNAs are part of RNAi. It is mainly pursued for cancer therapy. It is the new promising agent which can produce specific gene expression and also post transcriptional gene regulation process for disease treatment. In this current review I gathered lots of basic information about SiRNA like its structure, design, delivery system etc in short sweet manner.

CRISPR is an RNA guided genome editing technique of genetic engineering which works like genetic scissors. Based on simplified version of bacterial CRISPR-Cas9 antiviral defense system. It is more accurate, faster and cost efficient than other genome editing methods. There are two components in this system: First component includes a single guide RNA (sgRNA) of system which will identify target sequence in genome and Second component will include Cas9 nuclease of system which will act as a pair of scissors to spilt the double strands of DNA. CRISPR has promising therapeutic applications. This current review focuses on mechanism, therapeutic applications, delivery systems, limitations and different approaches used for gene editing using CRISPR.