fragile-X syndrome

fragile-X syndrome, a chromosomal disorder associated with a fragile site on the end of the X chromosome. The major symptom of the syndrome is diminished mental ability, which may range from mild learning impairment to severe intellectual disability (or mental retardation). The X chromosome is one of two sex chromosomes (the other being the Y chromosome). Males have one X and one Y chromosome; females have two X chromosomes. The male who receives the fragile-X...