Guanine hydrogen-bonding

Adenine and thymine hydrogen-bond with each other, and cytosine and guanine hydrogen-bond with each other. 

Figure 3.4 X-Ray structure of a cyclic hexamer containing cytosine-guanine hydrogen bonded links ...

Each base hydrogen bonds strongly to only its complementary base.Adenine hydrogen bonds to thymine or to uracil guanine hydrogen bonds to cytosine. 

Figure 25.9 Base pairing of adenine with thymine (a) and cytosine with guanine (b). The dimensions of the thymine-adenine and cytosine-guanine hydrogen-bonded pairs are such that they allow the formation of strong hydrogen bonds and also allow the base pairs to fit inside the two phosphate-ribose chains of the double helix. (Reprinted from Archives of Biochemistry and Biophysics, 65, Pauling, I., Corey,...

Fig.11 Representation of the cytosine-guanine hydrogen-bonded dimer and subsequent energy transfer from ZnP to H2P.

The DNA base pairs guanine (G), cytosine (C), adenine (A) and thymine (T). The uracil-2,6-diaminopyridine pair can also form three hydrogen bonds but has a much lower association constant than G-C. 

Figure 10.6 One sequence-specific interaction occurs more frequently than others in protein-DNA complexes two hydrogen bonds form between an arginine side chain of the protein and a guanine base of the DNA, as shown in this diagram.

The two strands which make up DNA are held together by hydrogen bonds between complementary pairs of bases adenine paired with thymine and guanine paired with cytosine. The integrity of the genetic code (and of life as we know it) depends on error-free transmission of base-pairing information. 

Examine AT pair and GC pair, adenine-thymine and guanine-cytosine base pairs, respectively. Identify the hydrogen bonds in each. Are they the same as those you sketched Are the base pairs flat as normally drawn in textbooks, or are they significantly puckered or twisted ... 

DNA is made up ot two intertwined strands. A sugar-phosphate chain makes up the backbone of each, and the two strands are joined by way of hydrogen bonds betwen parrs of nucleotide bases, adenine, thymine, guanine and cytosine. Adenine may only pair with thymine and guanine with cytosine. The molecule adopts a helical structure (actually, a double helical stnrcture or double helix ). 

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