(1986). Bailey and Scott’s Diagnostic microbiology. Alberts, B., Johnson, A., Lewis, J., Raff, M., Roberts, K., & Walter, P.-30 o twist angle 1.8 nm helix diameter.12 bp per turn 0.45 nm axial rise 45 o helix pitch 7 o base-pair tilt.It is long and thin as compared to B-DNA. Discovered by Rich, Nordheim &Wang in 1984.The cytosine in the adjacent nucleotide of Z-DNA is in the “normal” C2′ endo, anticonformation. The duplex in Z-DNA has to accommodate the distortion of this G nucleotide in the synconformation.Note that having the base in the anticonformation places it in the position where it can readily form H-bonds with the complementary base on the opposite strand. This places the guanine back over the sugar ring, in contrast to the usual anticonformation seen in A- and B-form nucleic acid.It has the sugar in the C3′ endoconformation (like A-form nucleic acid, and in contrast to B-form DNA) and the guanine base is in the synconformation.The big difference is at the G nucleotide.Z-DNA can form when the DNA is in an alternating purine-pyrimidine sequence such as GCGCGC, and indeed the G and C nucleotides are in different conformations, leading to the zig-zag pattern.Z-DNA is a radically different duplex structure, with the two strands coiling in left-handed helices and a pronounced zig-zag (hence the name) pattern in the phosphodiester backbone.34 o helix pitch -6 o base-pair tilt 36 o twist angle.9 nm (about 2.0 nm or 20 Angstroms) in diameter.34 nm between bp, 3.4 nm per turn, about 10 bp per turn.The base‑pairing scheme immediately suggests a way to replicate and copy the genetic information.
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