Single and double strand DNA breaks

[Andrew Karam <karam.1@osu.edu>]

Dear RADSAFERs -

One topic about which I am curious is that repair of double-strand DNA
breaks is so much more "iffy" than repair of single-strand breaks.  I
realize that SSBs are inherently easier to repair than are DSBs, but I am
wondering if there might be any additional factors.

For instance, it occurred to me that, until lungs and gills evolved (well
into the history of life) life would only have been exposed to
alpha-emitting atoms that happened to be within about a micron of the cell
(or algal mat or whatever).  This was the state of things for the first 3
billion years life existed.  After the evolution of gills and lungs, of
course, animals could pump large volumes of water or air past tender
internal tissues, increasing alpha exposure.  Could it be that alpha
radiation is so damaging simply because life didn't have to worry about
DSBs until relatively recently?

This is all speculation, of course; I would welcome any comments from those
of you who know more about this than I.

Sincerely,

Andy

The opinions expressed above are well-reasoned and insightful.  Needless to
say, they are not those of my employer. (with apologies to Michael Feldman)		

Andrew Karam, MS, CHP					(614) 292-1284 (phone)
The Ohio State University 					(614) 292-7002 (fax)
Office of Radiation Safety					"The mind is not a vessel to
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(karam.1@osu.edu)