Fragile X chromosome

    Fragile X chromosomes are characterized by satellites at the bottom ends of the long arm of a single metaphase X chromosome, which are seen in a conventional chromosome spread (inset, upper right), in the scanning electron micrograph, and in the Giemsa-banded chromosome (inset, lower right). The four banding regions are shown in the schematic diagram. The constriction at Xq2.6 is due to a long series of CGG triplet repeats. Fragile X is associated with Martin-Bell Syndrome, the most common form of inherited predisposition to mental retardation.

[For further information, see http://www.fragilex.org/index.htm]