Base pair transformations

The four types of mutagenic change are base-pair transformations, base-pair additions or deletions, large deletions and rearrangements, and unequal partition or nondisjunction. 

The first type of base-pair transformation may occur at any stage of the cell cycle. An example of such a... 

Another example is afforded by the mutagen and carcinogen vinyl chloride which is discussed in more detail in Chapter 7. This compound causes base-pair transformations, as a result of alkylation of N1 of... 

The second type of base-pair transformation, incorporation of an abnormal base analogue, only occurs at... 

The cycloreversion experiments showed a clean Tf=T-DNA to T/T-DNA transformation. No by-products were detected, which supports the idea that DNA may be more stable towards reduction compared to oxidation. Even heating the irradiated DNA with piperidine furnished no other DNA strands other then the repaired strands, showing that base labile sites - indicative for DNA damage - are not formed in the reductive regime. The quantum yield of the intra-DNA repair reaction was therefore calculated based on the assumption that the irradiation of the flavin-Tf=T-DNA strands induces a clean intramolecular excess electron transfer driven cycloreversion. The quantum yield was found to be around 0=0.005, which is high for a photoreaction in DNA. A first insight into how DNA is able to mediate the excess electron transfer was gained with the double strands 11 and 12 in which an additional A T base pair compared to 7 and 8 separates the dimer and the flavin unit. 

Steenken S (1988) Electron transfer between radicals and organic molecules via addition/elimina-tion. An inner-sphere path. In Rice-Evans C, Dormandy T (eds) Free radicals chemistry, pathology and medicine. Richelieu Press, London, pp 53-71 Steenken S (1989) Purine bases, nucleosides and nucleotides Aqueous solution redox chemistry and transformation reactions of their radical cations e and OH adducts. Chem Rev 89 503-520 Steenken S (1992) Electron-transfer-induced acidity/basicity and reactivity changes of purine and pyrimidine bases. Consequences of redox processes for DNA base pairs. Free Radical Res Commun 16 349-379... 

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