Apparently it is true. Your genes could have been altered even before your mother was born.
In December of 2013, there was a flurry of media activity reporting on a study published in Nature Neuroscience. Richard Gray, Science Correspondent for The Telegraph, describes the essence of the study:
Researchers at the Emory University School of Medicine, in Atlanta, found that mice can pass on learned information about traumatic or stressful experiences–in this case a fear of the smell of cherry blossom–to subsequent generations. The results may help to explain why people suffer from seemingly irrational phobias–it may be based on the inherited experiences of their ancestors.