COMMENT ON THE RATIO OF CHROMOSOME-TYPE DICENTRIC INTERCHANGES TO CENTRIC RINGS FOR TRACK-CLUSTERED COMPARED WITH RANDOM BREAKS

Evidence has been published suggesting that the ratio of chromosome-ty pe dicentric interchanges to centric rings (D/R or F) is significantly lower for neutrons than for X or gamma rays, and it is proposed that a low DIR could be used as a ''fingerprint'' for high-LET radiations. One explanation offered for this observation is that the closely space d, clustered breaks confined to linear tracks will favor intrachanges, as opposed to interchanges, leading to a lower D/R, while the more sc attered, random breaks of low-LET radiations will favor the reverse si tuation and elevate the DIR. We have tested this suggestion empiricall y by constructing various modeled tracks and grids of breaks which sat isfy the proposed conditions. These have then been superimposed, in ra ndom orientation, on an array of hexagons, representing a planar secti on through the interphase arm domains of 14 polarized, metacentric, G( 1)-phase chromosomes, and the D/R computed from the interaction of bre ak clusters with the arms. The ratios recovered were essentially the s ame for the four different break distributions tested, and we conclude that, for this simple model, the determinant of the DIR is the arm ar rangement in the array, rather than the disposition of the breaks. (C) 1996 by Radiation Research Society.