Watson and Crick's 1953 model describes B-DNA — the most common physiological form of DNA in aqueous solution at normal cellular conditions. B-DNA features: right-handed double helix, ~10.4 bp per turn, rise of 0.34 nm per base pair, major and minor grooves, antiparallel strands, and Watson-Crick base pairing (A-T: 2 H-bonds; G-C: 3 H-bonds). A-DNA occurs in dehydrated conditions; Z-DNA is left-handed; quadruplex DNA involves G-rich sequences in telomeres.