Linked genes are found close together on the same chromosome, and are inherited together more often than would be expected by chance. In fact, the closer they are to each other, the more likely it is that they will be inherited together. Researchers take advantage of linkage to determine a person's chance of developing a disease if the exact disease gene is unknown. To do this, they look at the DNA of people with the disease, and at the DNA of people who do not have the disease. They try to find certain genetic markers that are present more often in people who have the disease than in those who don't. This tells researchers that the disease-causing gene is located close to that genetic marker. Although researchers cannot give a genetic test for the disease gene, they can test for the genetic marker. People who have the genetic marker are more likely to have also inherited the disease-causing gene than people who do not have the genetic marker.