Frequency and distribution studies of asymmetrical versus symmetrical chromosome aberrations

Two aspects of the relationship between Asymmetrical (A) and Symmetrical (S) radiation-induced chromosomal aberrations are considered in this paper. (1) Are A and S truly alternative modes of lesion interactions? Relative frequencies for chromatid-type and chromosome-type are examined, and new lymphocyte data using banding is used to look at this, and also for parallelism in chromosome participation of the two forms for various aberration categories. All the tests applied suggest that A and S are alternative interaction modes. (2) The long-term survival characteristics of A and S are discussed, and the differences in expected frequencies of derived S per surviving cell from chromosome-type and chromatid-types are stressed. Since many in vivo tissues have varying mixtures of potential chromatid and chromosome aberration-bearing target cells, ultimate cell survival and derived S frequencies may differ between tissues for the same absorbed dose. An Appendix gives Relative Corrected Lengths (RCL) for chromosomes of the human karyotype which should be used when testing the various exchange aberration categories for random chromosome participation.