Heredity – “The biological process whereby genetic factors are transmitted from one generation to the next”
Epigenetic – arising from non-genetic external factors
If genes work as per environment, epigenetically, heredity too is environmental and not genetical.
So diabetes or any xyz body/mental condition is not because of genes but environment.
Subtly, our Pitru legacy is also part of environment and not part of genes (and so it is spiritual ritual and not just medical procedure).
Tarpana vidhi helps you to negate negative effects of environmental legacy.
PS: Talking about subtle environment when I consider heredity as environmental. Several set of genes are transmitted from our paternal and maternal lines. Beyond physical form i.e. air, water and solid.
Epigenetics: A Turning Point in Our Understanding of Heredity
In a study published in late 2011 in Nature, Stanford University geneticist Anne Brunet and colleagues described a series of experiments that caused nematodes raised under the same environmental conditions to experience dramatically different lifespans. Some individuals were exceptionally long-lived, and their descendants, through three generations, also enjoyed long lives. Clearly, the longevity advantage was inherited. And yet, the worms, both short- and long-lived, were genetically identical.