The ability of ionizing radiations of different LET to induce chromosomal deletions in Aspergillus nidulans
Mutation Research
I D Normansell, G Holt
Abstract
Conidia, derived from a strain of Aspergillus nidulans known to carry a specific chromosomal duplication, were irradiated. The duplicated segment had genetic markers, which, when eliminated from the genome, allowed the easy detection of deletion mutants. Survival curves derived following 15 MeV electron and gamma-ray irradiation were characterised by the presence of an appreciable shoulder, whilst 50 kvp X-rays gave a much smaller shoulder. Irradiation with beta-particles and alpha-particles gave rise to exponential survival curves. The RBE values for these radiations, based on the D37 value were for gamma-rays, 1.0, 15 MeV electrons 1.0, 50 kvp X-rays 1.9, beta-particles 2.1 and alpha-particles 3.4. With the exception of gamma-rays the radiations described were compared with respect to their ability to induce chromosomal deletions. When the number of deletants amongst survivors was plotted against dose, a linear relationship was found for electrons, X-rays and beta-particles. The response recorded for alpha-particles was essentially linear but with a biphasic component. The RBE values for the radiations, based on a value of unity for 15 MeV electrons were as follows: X-rays 1.3, beta-particles 0.8, alpha-particles above 7.5 kr...Continue Reading