Genetic research allowed to conclude that genes determine all peculiarities of functions for every particular human body including its diseases. A lot of mental conditions seem to emerge suddenly at some particular age; scientists cannot figure out which environmental factor contributed to their development, but these conditions pass in generations. That was the way people defined the cause behind hereditary diseases yet before the advent of genetic research. Later in the twentieth century, researchers proved that relatives with certain diseases have the same impaired gene at some segment of their chromosomes. This discovery automatically made children predisposed to many conditions and physical specifics immanent to their parents.
From the point of science, it will be correct to treat genes as a cause of diseases that run in generations. Genetic conditions may be inherited by some relatives but not by others; all in all, it is impossible to guess whether the diseases is present before tests diagnose it. In some cases, changing a lifestyle can help people avoid some conditions they are genetically predisposed to. Blaming genes in nasty disorders, patients frequently do not even realize that they can shape their own life with correct diet and lifestyle.
Taking into account the fact that genetic information is safely stored in our genome, people shall be more attentive to the external impacts they stand under. Our bodies naturally develop new mutations that will pass to the future generations. Everyone has to be alert about the heath risks they grant to the others, especially to their children.