单选题
The more medical science discovers about the complex interplay between nature and nurture, genetics and environment, the larger the role family history appears to play in disease. Last month's announcement that most of the 30, 000-plus genes in the human genome had been identified is likely to prompt a better understanding of family-related illness and new gene-based treatments. But until such treatments are available, people with a family history of certain diseases need to be watchful. They also need to remember that for most diseases, family history is not destiny. If you have what's known as a first-degree relative — a parent or sibling — who has been diagnosed with an illness, say, cancer, then your risk of developing the same illness rises. Having two affected first-degree relatives, or family members across generations — your mother and your grandmother — increases your risk further. "If the illness is occurring in multiple, close relatives, at younger ages than is typical for that disease, and over more than one generation, you have a truly problematic family history, says Robin Bennett of the Medical Genetics Clinic at the University of Washington Medical Center. In families afflicted with certain inherited disorders such as sickle cell anemia and cystic fibrosis, genes alone seem to determine who gets sick. But for most people, family history, lifestyle, and environment all influence which illnesses they develop, and at what age. Even if you have strong family history of, say, breast cancer, heart disease, or diabetes, taking advantage of the proven screening tests and treatments and changing your lifestyle may tip the odds back in your favor. Nearly everyone faces some kind of genetic risk. By comparing the health histories of twins with same genetic makeup, scientists have estimated the contribution genes make to trait like weight, cholesterol level, and blood pressure. Kenneth Kendler, a professor of psychiatry and genetics at the medical College of Virginia, has found that genes contribute heavily to some mental disorders, too. "We're pretty sure that with schizophrenia and bipolar disorders, 70 or 80 percent is inherited. Alcohol and drug dependence, 50 to 60 percent. Depression, 35 to 40 percent, . " Even so, he adds, "The strongest predictor of major depression is still your life experience. There aren't genes that make you depressed; there are genes that make you vulnerable to depression. "
单选题
Which of the following family histories is most indicative of your chance of developing the same disease?