Reply #8: the idea that ionizing radiation is highly mutagenic is basically wrong [View All]

[treepig]

that's because it damages many cellular components besides DNA. usually this damage is not a problem because it is biochemically identical to that caused by normal metabolism and a cell is well equipped to repair it, as discussed more at

http://www.lfr.com/news/EBulletins/e-bulletin016.htm

of course, at some point exposure to increasing levels of ionizing radiation overwhelms the cell's repair machinery. one consequence is that DNA damage goes unrepaired, which in turn could theoretically lead to mutations. however, at these doses, other cellular damage cannot be repaired either, and the cell usually dies (and at the organism level, acute radiation sickness results). there is really a quite tiny window of opportunity for radiation-induced mutations to actually occur.

most mutations occur from chemicals, such as those derived from cigarette smoke or diesel fumes, that selectively damage DNA over other cellular biomolecules. in this case, the cell can actually try to keep living and divide - to divide it must replicate it's DNA and if damage is present, this damage can lead to errors in replication that "fix" mutations into the genome. such mutations lead to outcomes such as cancer in people, or the ability of bacteria to live in nuclear power plants.

hence, the bacteria living in nuclear power plants do not gain their ability to live there because of radiation-induced mutations - instead they are able to survive because of pre-existing mutations from other sources such as chemicals or sunlight. as far as the chernobyl exclusion zone goes, the level of radiation in most areas is low enough to have little biological consequence - hence the animals flourish simply because humans have "excluded" themselves. it's really quite an interesting observation that the worst nuclear power plant accident in history is less damaging to the environment than the usual day to day activities of people.