According to Fred Wright, North Carolina State University professor of statistics and biological sciences, director of NC State's Bioinformatics Center and co-first author of the study, said everyone has the same set of genes. It's difficult to determine which genes are heritable, or controlled by your DNA, versus those that may be affected by the environment.
He said teasing out the difference between heredity and environment is key to narrowing the field when you're looking for a genetic relationship to a particular disease.
Wright, with co-first author Patrick Sullivan, Distinguished Professor of Genetics and Psychiatry at UNC-Chapel Hill and director of the Center for Psychiatric Genomics, and national and international colleagues, analyzed blood sample data from 2,752 adult twins (both identical and fraternal) from the Netherlands Twin Register and an additional 1,895 participants from the Netherlands Study of Depression and Anxiety.
For all 20,000 individual genes, they determined whether those genes were heritable - controlled by the DNA "dimmer switch" - or largely affected by environment.
"Identical twins have identical DNA," Wright explains, "so if a gene is heritable, its expression will be more similar in identical twins than in fraternal twins. This process allowed us to create a database of heritable genes, which we could then compare with genes that have been implicated in disease risk."
The study has been published online in the journal Nature Genetics.