It was reported that the crotamine gene was isolated twice from two different specimens, one in a method that resulted in a gene size of 1.8 kbp and in the other specimen a gene size of 1.1 kbp. The gene has been previously isolated in the "C. durissus terrificus" genome and the protein itself belongs to a group of small basic polypeptide myotoxins (SBPM). The contents of Crotalus venoms can vary according to subspecies and geographical location. The Crt-p1 gene, as described by Radis-Bastista et al. 2003, consists of about three exons separated by one short phase-2 (140 bp) and one long phase-1 (900 bp) intron. Exon 1 codes for the first 19 amino acids of the signal peptide and includes the 5’-untranslated region. Exon 2 codes 39 amino acids to the mature crotamine and three signal peptide amino acids. Exon 3 codes for the terminal lysine and the last three amino acids of the mature toxin. Research on SBPM amino acid sequences among different Crotalus species has revealed a high degree of likeness ranging from 83% - 98%.