Candidate genes are genes that are selected based on their known function or location within a certain region of interest in the genome. These genes are believed to play a role in a particular trait or disease, making them potential targets for further study. By focusing on candidate genes, researchers can narrow down their search for genetic factors that may be responsible for a specific phenotype or condition. This approach can help to identify new pathways and mechanisms underlying complex traits and diseases. Candidate gene studies are often used in conjunction with genome-wide association studies to identify genetic variants associated with a particular trait or disease.