Adenine-guanine base pair

Adenine-guanine base pairs occupy more space than is available in the interior of the double helix, whereas cytosine—thymine base pairs are too small to span the distance between the sites to which complementary bases are bonded. One would not normally expect to find such base pairs in DNA. 

A crosslinking mechanism based on these data was proposed. Initial monoalkylation at guanine is followed by a template-directed alkylation at either guanine or adenine two base pairs away on the opposite strand. In support of this, Armstrong... 

The bases found in RNA (ribonucleic acid) are the purine heterocyclics adenine (6-aminopurine) and guanine (2-amino-6-oxypurine) and their complementary pyrimidine bases uracil (2,4-dioxypyrimidine) and cytosine (2-oxy-4-aminopyrimidine), respectively (Section 1, Appendix). In RNA double-stranded duplexes adenine (A) base-pairs with uracil (U) via two hydrogen bonds (A=U) and guanine base-pairs with cytosine (C) via 3 hydrogen bonds (G=C). Adenine forms the nucleoside adenosine by an N-glycosidic link with the... 

Gould, I. R. and Kollman, P. A., Theoretical investigation of the hydrogen bond strengths in guanine-cytosine and adenine-thymine base pairs, J. Am. Chem. Soc. 116, 2493-2499 (1994). 

Considerable attention has also been devoted by several investigators to the theoretical study of the potential curves for hydrogen bonds of the guanine-cytosine and adenine-thymine base pairs. An accurate representation of this potential is important because the genetic code is contained in this interaction. Lowdin has suggested that mutations may be a result of a shift in position of the hydrogen bond protons in the base units of DNA via proton tunneling. " The idea of proton... 

Yet another effect of the action of Ag" has been described, namely, its interaction with nucleic acids [112]. The Ag" ion interacts preferentially with the bases found in DNA rather than with the phosphate group [113-118]. The reaction between Ag and a GC (guanine-cytosine) base pair proceeds via two steps, whereas that between Ag" and an AT (adenine-thymine) base pair requires only one step [116], Ag appears to be attached to the N atom... 

Base pairing The hydrogen bonds formed between complementary bases that are part of the polynucleotide chains of nucleic acids. The base pairing is specific in that adenine will base pair with thymine (uracil in RNA) and guanine will pair with cytosine. 

D Molecules Adenine-thymine base pair Guanine-[Pg.1121]

Problem 21.57. At high temperatures, deoxynucleic acids become denatured, i.e., they unwind from double helices into disordered single strands. Account for the fact that the higher the content of guanine-cytosine base pairs relative to adenine-thymine base pairs, the higher the temperature required to denature a DNA double helix. 

Complexes of pentahydrated Zrf with guanine, adenine, and the guanine-cytosine and adenine-thymine base pairs. Structures and energies characterized by polarizable molecular mechanics and ab initio calculations "... 

To account for the observed base ratios and uniform thickness of DNA, Watson and Crick postulated that purine and pyrimidine bases project inward toward the axis of the helix and always pair in a specific manner. According to scale models, the dimensions of an adenine-thymine base pair are almost identical to the dimensions of a guanine-cytosine base pair, and the length of each pair is consistent with the core thickness of a DNA strand (Figure 20.7). Thus, if the purine base in one strand is adenine, then its complement in... 

How many hydrogen bonds link a guanine-c)ftosine base pair an adenine-uracil base pair Would you expect any difference in strength between guanine-cytosine bonding and adenine-uracil bonding Explain. 

How many hydrogen bonds link an adenine-thymine base pair Would there be any difference in strength between adenine-thymine bonding and adenine-uracil bonding between adenine-thymine and cytosine-guanine bonding Explain. 

BrdUrd is a well-known mutagen causing base-pairing errors, which result mainly in transition of the adenine-thymine base pair to guanine-cytosine. BrdUrd also induces SCEs, causes chromosome aberrations, increases radiosensitivity, alters binding affinity of chromatin proteins, and has several other effects on cells that may or may not be related to its substitution into DNA. Thus, it is possible that cells containing BrdUrd do not show the same response to chemicals in terms of SCEs, aberrations, or mutations as do untreated cells. 

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