Interestingly, the USH syndrome is a recessive genetic disorder, which may suggest that USH1 syndrome can be classified as a group III disease, but the SF2 values assessed in the present study in the USH1 cells were found to be between 18 and 22%, i.e., corresponding to the cellular radiosensitivity of the genetic diseases belonging to group II of radiosensitivity, such as HD, TSC, NF1, and XPD [26,27,28,29]. This evidence concerns the gene NF1 and Huntington disease.