Fragile X Mental Retardation 1 (FMR1)

FMR1 is normally made in many tissues, especially in the brain and testes. It may play a role in the development of synaptic connections between nerve cells in the brain, where cell-to-cell communication occurs. The connections between nerve cells can change and adapt over time in response to experience (a characteristic called synaptic plasticity). FMRP may help regulate synaptic plasticity, which is important for learning and memory.

One region of the FMR1 gene contains a 3 base Variable Number Tandem Repeat (VNTR, or more specifically, a trinucleotide repeat). The sequence CGG is repeated a number of times. In most healthy individuals, the number of CGG repeats ranges from fewer than 10 to about 40, with the median at about 29 repeats.