It is a well accepted assumption that the transcription of DNA is done along a single strand (TOCCHINI-VALENTINE and cols.1, SPIEGELMAN and HAYASHI 2, MARMUR 3 and TOHÁ C. 4) and that the biosynthetic mRNA obtained is monoteonic and is read in a linear fashion during the process of translation. In order to have a good interaction with the ribosome and an easy reading of the message the mRNA should remain extended (OKAMOTO and TAKANAMI5; KHORANA6). We assume that this state is due to a lack of complementary zones in the strand of mRNA. If the assumption is valid, we can imagine that the sequences of basis in the messenger is substantially limited by this restriction that excludes the existence of complementary zones.