How much do you know about your mom's health? What about her mom's? Or your dad's mom's? A genetic predisposition seriously ups your own cancer risk. What's more, while only 5 to 10 percent of breast cancers are hereditary, they can be way more aggressive than non-inherited types. What you find might be scary, but as Angelina Jolie proved, you'll still have risk-reducing options. Here, your pressing gene questions, answered. How do I know if I inherited a high breast-cancer risk?