Turner Syndrome
Turner syndrome is caused when nondisjunction produces a gamete with no sex chromosomes. When this gamete fertilizes a normal gamete containing one X chromosome, it results in an XO (the O means there is no second sex chromosome) female with only 45 chromosomes. The X chromosome that is inherited can be either maternal or paternal, although it is usually maternal in origin. XO individuals are female because they have no Y chromosome.
Females with Turner Syndrome are usually shorter than average, and have abnormal ovarian development. Other physical features such as webbed neck, as well as kidney, thyroid, heart and skeletal disorders vary among individuals and are generally not serious. XO women have normal intelligence and with proper treatment can expect to live a normal lifespan.