Overview of repeats
FRAXE mental retardation (FRAXE) is caused by CCG repeats in the AFF2 gene (also known as the FMR2 gene). Knight et al. (1993) found that in all male patients at least 200 repeats were present. Also, carrier females with over 200 repeats could have mental impairment. Repeat range in the control group was between 6 and 25 repeats (Knight et al., 1993).