In investigating the regulatory characteristics that contribute to the stability and evolutionary conservation of gene expression, we quantified the differences in genetic background between individuals in the medaka (O. latipes) inbred strain and between wild strains by genome resequencing. The inbred (Hd-rR) samples consisted of two males and two females, which were born on the same day from the same parents. For each wild strain, one male individual was sampled. Each sample was derived from an individual at the juvenile stage, and DNA was extracted from half the body.