title: Heteronomous DNA.
abstract: A fibrous form of poly d(A):poly d(T) has a heteronomous secondary structure which is the first to be confirmed for a polynucleotide duplex: although both chains are 10(1) helices, mutually hydrogen-bonded in the standard (Watson-Crick) fashion, each has a quite different conformation. One chain -- probably poly d(A) -- has C3'-endo-puckered furanose rings characteristic of the A family of polynucleotide secondary structures while the other -- probably poly d(T) -- has the C2'-endo-puckered rings of the B family. Since analogous heteronomous structures could be assumed by DNA-DNA or DNA-RNA duplexes containing more general base sequences the polymorphic range of polynucleotide double-helices may be even greater than we have come to suppose.
mesh_terms: D003460:Crystallization; D004247:DNA / Q000032:analysis*; D008433:Mathematics; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D011067:Poly dA-dT / Q000032:analysis; D014961:X-Ray Diffraction
chemical_list: D011067:Poly dA-dT; D004247:DNA