I would think lower wavelength EM radiation would be screened by the
massive clumps of DNA that exist in a eukaryotic cell, especially
non-coding sequences which(interestingly enough) tend to clump up to a very
high degree in a bundle of nucleotides and histones. Maybe the low
wavelength I'm talking about it not very common (cosmic/gamma rays, maybe?)
> The idea you have would have two main requirements:
>
> 1) The exposure of the cell to the mutagen cannot depend on the amount of
> DNA in the cell. Direct radiation is out, although free radicals from
> radiation would be OK.
Along with free radicals from metabolic processes, free radicals from the
environment, and other chemical mutagens.
> 2) The mutagen must be largely eliminated by mutating DNA. If the mutagen
> is largely cleared by any other process, increasing DNA will just
increase
> the proportion "cleared" by affecting DNA. Also, if the mutagen is
> not destroyed or inactivated by mutating DNA, then obviously extra DNA
> doesn't help.
>
> The only mutagen I know of that would meet qualification 2 is other DNA.
Try most carcinogens. Most carcinogens work by binding to areas of DNA
during cell division. The replication process has to skip this part of the
DNA, causing a massive deletion. Obviously, if such a mutagen is bound, it
will only mutate that particularly area, and no others. Thus, it is
"cleared" in this sense.
hmmm... I think I may have something there, what do you think?
> The idea that "junk" DNA provides a distraction for all those transposons
> hopping around has been suggested, although I don't know where.
Also a good explanation. A good way to test this hypothesis would be to
look for transposon binding/recombination sequences in junk DNA.
Geoff.