Figure 1.

X-chromosome inactivation in females with fragile X syndrome and corresponding production of fragile X mental retardation 1 (FMR1) protein in each cell. (A) Group of progenitor cells. (B) Each cell contains two X chromosomes. The unaffected chromosomes are shown in solid green, and affected chromosomes are depicted with a red band. (C) One of the two chromosomes in each cell will be silenced at random indicated with red shading. In cells where the affected chromosome is silenced, there is normal production of the FMR1 protein. In cells where the unaffected chromosome is silenced, there is reduced production of the FMR1 protein. FMR1: fragile X mental retardation 1; FMRP: fragile X mental retardation protein.