Nonoverlapping A U ACG AG U C code 1 2 3 Overlapping A UACGAGU C de Amino acid sequence studies of tobacco mosaic virus mutants and abnormal hemoglobins showed that alterations usually affected only one single amino acid: genetic codes are nonoverlapping.Amino acid sequence studies of tobacco mosaic virus mutants and abnormal hemoglobins showed that alterations usually affected only one single amino acid: genetic codes are nonoverlapping