FMR1 and fragile X syndrome: Fragile X Syndrome (FXS) is caused by meiotic instability in the 5′ untranslated region of the X chromosome-linked Fragile X messenger ribonucleoprotein 1 gene (Fmr1), impeding the transcription of the Fragile X Messenger Ribonucleoprotein (FMRP) (Suardi and Haddad, 2020).