Gene discovery is the process of identifying genes that contribute to the development of a trait or phenotype. Researchers often try to discover the genes that are involved in specific diseases. They also try to find the genes that contribute to many other traits.

Polymorphic markers along the chromosomes (here shown as different colored bars) are examined to determine which is coinherited with the disease (shaded circle and square). The red marker in the third position is found only in the two family members with the disease.

Gene discovery begins with clearly defining a trait of interest and determining if that trait has a genetic and/or environmental basis. This is done using several approaches, such as sibling recurrence risk ratio, familial aggregation, and twin and adoption studies. The sibling recurrence risk ratio is the frequency of a disease among the relatives of an affected person...