grotein, Dilterent poimt muthitions in the SCNYA gene were tdentitied in three farnilies with the condition. In Family 1. a C-to-T substitution in exon 15 vields a 898-amino acid protcin. in Family 2. deletion of a single base results in a 766-amino acid protein. In Family 3. a G-to-A substitution in exon 10 yields a 458 -amino acid protein. a. The codon mutated in Family 1 , and the codon mutated in Family 3 is ,osity for extremely rare mutations in a human gene called SCN9A causes com. ivity to pain and a total lack of the sense of smell. The gene encodes a 1977-am Different point mutations in the SCN9A gene were identified in three families w an. In Family 1, a C-to-T substitution in exon 15 yields a 898-amino acid protein. n of a single base results in a 766-amino acid protein. In Family 3, a G-to-A substi 0 yields a 458 -amino acid protein. ie codon mutated in Family 1 is , and the codon mut.