"CRISPR" stands for Clustered Regularly Interspaced Short Palindromic Repeats, which are the hallmark of a bacterial defense system that forms the basis for CRISPR-Cas9 genome editing technology. In the field of genome engineering, the term "CRISPR" or "CRISPR-Cas9" is often used loosely to refer to the various CRISPR-Cas9 and -CPF1, (and other) systems that can be programmed to target specific stretches of genetic code and to edit DNA at precise locations, as well as for other purposes, such as for new diagnostic tools. How can this tool be used to alter genes in various organisms?

by designing short guide RNAs (sgRNAs) customized to target genes of interest in the cells of these species

Explanation:

The CRISPR-Cas9 editing system is a versatile and powerful genome engineering tool for editing genomes, which can be directed to alter almost any DNA sequence in order to modify gene function. This system consists of an endonuclease protein (Cas 9) that cuts DNA at specific sites guided by a short guide RNA (sgRNA), which binds by base complementarity to the target sequence. This sgRNA must be designed with efficiency and specificity to target genes of interest. In consequence, the CRISPR-Cas9 genome editing system produces DNA double-strand breaks which may be repaired by 1- error-prone nonhomologous end joining (NHEJ) or 2-homology-directed repair (HDR) DNA repair pathways. According to the DNA repair pathway that has been activated, it is possible to trigger genetic modifications in the cells of different species (i.e., plant cells, animal cells, human cells, etc).