Cows already have the dna that encodes for NRAMP1, but in order to demonstrate their prowess with CRISPR technology, this group 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. This seems to have been the case.
So here, 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, thus conferring some tuberculosis resistance by means of allowing the cows white blood cells to produce nitric oxide more efficiently.
"Ishee was preparing for a project that sought to cure hyperuricemia in Dalmatians—a common liver malfunction that frequently results in kidney stones, bladder stones or gout.
"It should be straight forward," he told Gizmodo. Ishee plans to use the gene-editing technique CRISPR to correct the single errant nucleotide that causes the condition, reversing the mutation to turn a T in the genetic code back into the correct G. Then he'll use a technique called sperm-mediated gene transfer, which will allow him to transfer his engineered Dalmation DNA to a female Dalmation, resulting, he hopes, in a fertilized egg that'll produce hyperuricemia-free pups.
"The animals just get molecular surgery to fix a broken gene that causes their bladders to explode," he said. "Then those animals can become the founders on a healthy generation of Dalmatians and breed the disease away in a few years.""
I've read there's a single base that makes cow's milk to behave like that.