A synthetic transfer RNA with an extended anticodon loop. A synthetic suppressor transfer RNA useful for the treatment of a genetic disease like cystic fibrosis associated with a nonsense mutation. The synthetic transfer RNA contains an extended anticodon loop with two consecutive anticodon base triplets configured to base-pair to two consecutive codon base triplets on an mRNA. The first anticodon base triplet or the second anticodon base triplet is configured to base-pair to a stop codon base triplet on the mRNA.