Induction of chromosome aberrations by X-rays and chemical mutagens in a desynaptic mutant and in wild-type barley

Abstract

It has previously been proposed that eukaryotes with a genetically determined abnormality in the sequence of events leading to normal chromosome exchange at meiosis, might be expected to show an altered response on the part of their somatic cell chromosomes following exposure to chemical or physical mutagens. As part of a programme undertaken to examine this contention, dry and soaked seeds of a wildtype ( Ds Ds) and a desynaptic mutant ( ds ds) of barley were exposed to X-rays and the frequency of chromosome-type aberrations determined in cells in their first post-irradiation mitosis. Preliminary experiments with these materials by Riley and Miller had pointed to an increase in yield of aberrations in cells of the mutant relative to the normal, but no such difference could be demonstrated in the present more extensive experiments. Seeds and root-tips were also exposed to the chemical mutagens nitrogen mustard and diepoxybutane and a detailed analysis of the induced chromatid-type aberrations revealed no difference in the sensitivity of ds ds and Ds Ds genotypes. The frequency of sister chromatid exchange were studied in autoradiographs of root-tip cells in their second mitosis following exposure to [ 3H]thymidine. There was no difference in the incidence of such exchanges between cells from the different genotypes.