confers resistance to tuberculosis in cows

Cows have the protein NRAMP1 in their white blood cells that helps in the production of nitric oxide (a molecule that is toxic to bacteria, including tuberculosis). It has been shown that if you have more of the protein, then you tend to be more resistant to tuberculosis infection, and less of the protein, then you are less resistant to a tuberculosis infection.1

NRAMP1 is a transmembrane iron transporter. Cows already have the dna that encodes for NRAMP1, but in order boost their resistance to tuberculosis (as well as demonstrate their facility with CRISPR technologies), Gao et al. found a dormant location in the cow’s genome in order to insert DNA that encodes a second copy of the same protein. The expectation being that by having a duplicate copy of the DNA that encodes for the NRAMP1 protein, more of the protein would be produced, and the cows would be less susceptible to tuberculosis. Adding DNA encoding a protein that already existed in the cow’s genome allowed more of the protein (NRAMP1 - an iron transport machine) to be produced, conferred some tuberculosis resistance by means of allowing the cows white blood cells to produce nitric oxide more efficiently.2