Our lifestyles and environment can change the way our genes are expressed, leading even identical twins to become distinct as they age.

NOVA is produced by WGBH in Boston. Funding for NOVA scienceNOW is provided the National Science Foundation, the Howard Hughes Medical Institute, the Alfred P. Sloan Foundation, the Corporation for Public Broadcasting, and public television viewers.

This material is based upon work supported by the National Science Foundation under Grant No. 0407101. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.