The 2007 "Nova" episode "The Ghost in Your Genes," delivered big news: Your DNA contains chemical markers that allow genes to be turned on and off.

That means, at least for some inherited characteristics, you're not condemned to their preprogrammed influence.

This was dubbed "epigenetics," and it's now widely acknowledged that a person's lifestyle choices can turn off some harmful predispositions for health problems.

The opposite is true, too. You can cause genetic switches to get thrown that create health problems (obesity does that) and then pass those problems on to future generations.

In one recent study on the power of smart lifestyle choices to dismiss genetically predisposed health problems, researchers looked at data from almost half a million men and women who didn't have current heart problems, but who had a family or genetic history of heart disease.

The researchers found that regular exercise lowered participants' risk for heart problems.

A strong (instead of weak) grip lowered participants' risk of coronary heart disease by 36 percent and of atrial fibrillation by 46 percent.

Furthermore, high fitness levels were linked to a 49 percent lower risk for coronary heart disease and a 60 percent lower risk for atrial fibrillation.

So if your relatives had heart woes, start an exercise regimen and upgrade your diet, too, so it eliminates highly processed foods, red meats, and added sugars.