DIFFERENT BIOLOGICAL SPECIES BROADCAST THEIR DNAS AT DIFFERENT (G+C)PERCENT WAVELENGTHS

Radio can be used as a metaphor for the transmission of information by DNA through time and space. Just as different radio transmitters broa dcast at different wavelengths to prevent interference, so different b iological species ''broadcast'' their DNAs at different (G + C)% ''wav elengths'' to prevent recombination. It is postulated that species dif ferences in (G + C)% prevent recombination. First, evidence is present ed supporting the early Crick-Sobell stem-loop model for genetic recom bination, which proposes that the rate-limiting step in recombination is the recognition (''kissing'') of complementary sequences in the loo ps of stem-loop structures extruded from supercoiled DNA. Then, variou s ways in which differences in (G + C)% might impede complementary loo p interactions are outlined. The strength of the postulate is that it brings together a variety of disparate observations in fields that hav e not previously been seen as related. Thus, explanations are apparent for why most mutations are not selectively neutral (the ''neutralist/ selectionist'' debate), why introns were present in the earliest genes (the ''introns-early/introns-late'' debate), and the origin of specie s. (C) 1996 Academic Press Limited