Previously it was thought that only 2% of our DNA is meaningful and the remaining 98% is non-coding "junk". But today we are beginning to know how the junk part of our DNA works to decide our personal characteristics and tendencies.
In the non-coding 98% of our DNA, we have countless switches to promote or suppress the physiological reactions of our bodies. Interestingly, we can change the states of these switches through our own efforts and even can affect the DNA conditions of our offspring before their birth.