Modern medical studies have shown that human disease results from genetic and/or environmental causes. With our increasing ability to control infectious and nutritional diseases worldwide, genetic diseases increasingly impact upon human health and life, both physically and psychologically. Genetic diseases (or genetic disorders) are frequently old diseases with newly understood causes, these being one or more abnormalities in an individual’s genome, and they may present from early embryonic development to postnatal life. Cancers fall into the genetic disease category, because of acquired somatic mutations produced by genomic instability, and also inherited gene mutations, as occurs in about 5-10% of cases. Studies have also demonstrated that genetic defects are the major known cause of pregnancy loss in developed nations, and almost half of all spontaneous abortions (miscarriages) involve a chromosomally abnormal fetus. It will be rare for any family to be entirely free of genetic disease, and genetic diseases therefore impose a huge burden upon individuals, families and societies.