In biology, the SECIS element (SECIS: selenocysteine insertion sequence) is an RNA element around 60 nucleotides in length that adopts a stem-loop structure. This structural motif (pattern of nucleotides) directs the cell to translate UGA codons as selenocysteines. (UGA is normally a stop codon.) SECIS elements are thus a fundamental aspect of messenger RNAs encoding selenoproteins, proteins that include one or more selenocysteine residues.