Ionizing radiation mutagenesis induced

Mutagenesis can occur as the result of exposure to ionizing radiation and certain chemicals. Ionizing radiations include cosmic rays, x rays, and ultraviolet light. It is of interest to note that melanoma, caused almost exclusively by exposure to the ultraviolet radiation from the snn, is the most rapidly increasing lethal cancer in the United States. In melanoma, ultra violet radiation induces what is called thymine dimers. This means that two thymine nucleotides next to each other in a DNA sequence form an abnormal bond. Thymine dimers in a... 

The original Larkin and Scowcroft paper also espoused the exploitation of somaclonal variation in crop improvement. It has been argued that using tissue culture to induce mutations is operationally and perhaps even mechanistically equivalent to mutagenesis via chemicals or ionizing radiation. A small number of papers have recently appeared, however, which demonstrate that the frequency and spectrum of mutants generated via mutagens vs. cell culture are indeed different (16). 

Much of the biochemistry and biophysics of DNA relies on the electron donating properties of nucleotides, which, in the simplest sense, are reflected in ionization energies. For example, electron donation, as reflected in the susceptibility of nucleotides to electrophilic attack, plays a ubiquitous role in mechanisms of chemical mutagenesis and carcinogenesis (1,2). Similarly, nucleotide ionization is an initiating step associated with radiation induced DNA strand scission (3-6). Nucleotide electron donation and ionization is also central to mechanisms responsible for electron transport in oligonucleotides (7). 

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