Using both cloning and DNA sequencing, researchers ruled out five genes (of an identified 31 candidate genes) as the causative gene for Progressive Rod-Cone Disease (PRCD), a form of Progressive Retinal Atrophy, an inherited disease that leads to blindness. With continued research, the cloning and sequencing of the other 26 candidate genes can be completed. Once the genetic cause and mutation are found, direct DNA tests, which are more accurate than linkage tests, can be developed to help breeders make breeding decisions in order to reduce or eliminate this disease. All 31 candidate genes were known to be in the region of the chromosome linked to PRCD by researchers at Cornell.