Twins sisters Leah and Lily know that heart disease runs in the family. Both sisters like to exercise, but Lily also has a high-stress job, has new born twins, and only sleeps about 2 - 3 hours a night. Leah is a yoga instructor, does not have any children, and eats a mostly vegetarian diet. The field of epigenetics would suggest:

The environment can alter gene expression, changing both women's risk of heart disease.

Explanation:

Epigenetics studies an organism's change as a result of modification in his gene expression while his genetic code remains the same. Epigenetics controls normal development and homeostasis that would have been defined by the natural genes of a person, characterized by DNA and chromatin modifications(and all related systems).

Environmental factors that have become lifestyle habits are identified as some things that might modify epigenetic patterns. They include: diet, obesity, physical activity, tobacco smoking, alcohol consumption, environmental pollutants, psychological stress, and over working such as doing night shifts.