MUTAGENESIS IN CAENORHABDITIS-ELEGANS .2. A SPECTRUM OF MUTATIONAL EVENTS INDUCED WITH 1500-R OF GAMMA-RADIATION

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  • 1 January 1985
    • journal article
    • research article
    • Vol. 109  (3) , 493-511
Abstract
A .gamma.-ray dose-response curve was established for recessive lethal events (lethals) captured over the eT1 balancer. The nature of lethal events produced, with a frequency of 0.04 per eT1 region, were analyzed at a dose of 1500 r. A protocol was developed that, in the absence of cytogenetics, allows balanced lethals to be analyzed for associated chromosomal rearrangements. A set of 35 lethal strains was chosen for the analysis. Although the dosage was relatively low, a large number of multiple-break events were observed. The fraction of lethals associated with rearrangements was found to be 0.76. Currently most X- and .gamma.-ray dosages used for mutagenesis in C. elegans are 6000-8000 r. From the data, a conservative estimate was that 43% of rearrangements induced with 8000 r would be accompanied by additional chromosome breaks in the genome. With 1500 r the value was 5%. The 35 lethals studied were derived from 875 screened F1. Among these lethals there were at least 2 unc-36 duplications, at least 4 translocations, at least 6 deficiencies of chromosome V (these delete about 90% of the unc-60 to unc-42 region) and several unanalyzed rearrangements. It is possible to recover desired rearrangements at reasonable rates with a dose of only 1500 r. The levels of ionizing radiation employed in most published C. elegans studies are excessive and efforts should be made to use reduced levels in the future.