April 2019

Genome editing (also known as gene editing, genome engineering, genetic engineering) refers to a set of tools and techniques that allows researchers to manipulate the underlying genetic code of an organism. These changes can include adding, removing or making specific modifications to targeted regions in the genome. Although a number of methods exist for genome editing, the potential promise and quick rise to popularity of the CRISPR-Cas9 approach, which stands for Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR associated protein 9, has placed it front and center in the public eye.

CRISPR-Cas9 was originally discovered in bacteria where it protects against viruses in a similar way to how our immune system operates. By storing short pieces of DNA from the viruses, the bacteria are able to recognize viruses that have infected them before and produce short RNA sequences that match the viruses' DNA. These short RNA sequences bind to Cas9, or other CRISPR associated proteins, which are able to cut both strands of the targeted DNA. If the virus is unable to correctly repair these cuts, it usually dies. Much like in the bacteria, researchers are able to create short RNA sequences that bind to Cas9 and guide it to specific locations of interest within an organism's genetic code. Once a cut is made, researchers rely on the cell's own DNA repair mechanisms to make the desired manipulations (add, remove or modify).

By Blythe Schultz and Jason W. Ross
Iowa State University Department of Animal Science Iowa Pork Industry Center
National Hog Farmer