Candidate gene refers to a specific DNA sequence that is believed to have an association with a particular disease or condition. These genes are identified through various methods, such as family studies, linkage analysis and association studies, which suggest that they may play a role in the development of a disorder. Candidate genes are then tested for their involvement in the disease by conducting experiments to see if changes or mutations occur more frequently in individuals with the condition compared to those without it. If these genetic variations are found to be associated with the disease, they may provide valuable insights into its cause and potential treatments.