Gene manipulation tools have transformed biomedical research and improved the possibilities of their uses for therapeutic purposes. These tools have aided effective genomic modification in many organisms and have been successfully applied in biomedical engineering, biotechnology and biomedicine. They also shown a potential for therapeutic applications to alleviate genetic and non-genetic diseases. Small interfering RNA (siRNA) and clustered regularly inter-spaced short-palindromic repeat/associated-protein system (CRISPR/Cas) are two of the tools applied in genetic manipulation. This review aims to evaluate the molecular influence of siRNA and CRISPR/Cas as novel tools for genetic manipulations. This review discusses the molecular mechanism of siRNA and CRISPR/Cas, and the advantages and disadvantages of siRNA and CRISPR/Cas. This review also presents comparison between siRNA and CRISPR/Cas as potential tools for gene therapy. siRNA therapeutic applications occur through protein knockout with- out causing damage to cells. siRNA knocks down gene expression at the mRNA level, whereas CRISPR/Cas knocks out gene permanently at the DNA level. Inconclusion, gene manipulation tools have potential for applications that improve therapeutic strategies and plant-derived products, but ethical standards must be established before the clin- ical application of gene editing.