What Are Genetic Disorders ? According to the National Human Genome Research Institute, a genetic disorder is a "disease caused in whole or in part by a change in the DNA sequence away from the normal sequence."Our book "Guide to the Most Common Genetic Disorders (Symptoms, Causes/Genetic profiles, Types and Inheritance)" is written in outline format for ease of use. It is of great value to medical geneticists, genetic counselors, pediatricians, neonatologists, developmental pediatricians, perinatologists, obstetricians, neurologists, pathologists, and any physicians and health care professionals caring for handicapped children such as craniofacial surgeons, plastic surgeons, otolaryngologists, and orthopedists. It is the definitive volume for helping all physicians to understand and recognize genetic diseases and malformation syndromes and better evaluate, counsel, and manage affected patients.There are a number of the most common genetic disorders that can commonly occur in people. Here are just many of them and everything that you need to know about them. Just we divided the text to many parts according to alphabet diseases that is the PART ONE.