New advances in genetics have dramatically expanded opportunities to avoid, prevent, diagnose and even treat a wide range of genetic disorders. Now, more than ever before, families need to be alert about the implications and applications of these new developments and discoveries. Few are aware that apparently quite different disorders in their family may be caused by the same gene mutation. Even fewer know that there are some 7,000 rare genetic diseases with about 1 in 12 of us being affected by one of these inherited or sporadically occurring genetic disorders. In non-technical language, the author has provided a valuable guide to why and what you should know about disorders of genes and chromosomes and the many available options. The histories of families discussed and seen in consultation by the author were selected for the, often poignant, lessons they teach about the lifesaving importance of knowing one's family history and ethnic origin. The ongoing cascade of new DNA tests already enable a host of evaluations that establish precise diagnosis, detection of mutation carriers, enable prenatal or preimplantation diagnosis, determine sensitivity to certain medications, recognize genetic susceptibility and accurately predict a genetic disorder where prevention or intervention is possible. A host of common genetic disorders that occur in families described in this book include cancer, diseases of the heart and blood vessels, strokes, disorders of the brain and nervous system, disorders related to ethnicity, autism, mental illness, birth defects, mental retardation, bleeding and clotting disorders, as well as the all too common diabetes, obesity and hypertension, as well as many other conditions. So often when facing serious to grim test results, many families have expressed the sentiment "If we had only known." Not infrequently, this sadness has reflected the lack of family communication and the common tendency to delay seeking genetic evaluation and counseling. Indeed, the vast majority of people in all countries have not consulted a clinical geneticist when the need was evident. The message of this book is clear and the guidance authoritative and explicit. Know your family history, be cognizant of your ethnic origins, seek appropriate consultations and opt for meaningful genetic tests. By knowing your genes, you will help secure your health, and even save your life and the lives of those you love.