The gemini-XI S-4 spaceflight radiation interaction experiment. II. Analysis of survival levels and forward-mutation frequencies in Neurospora crassa.

Samples of asexual spores of a two-component heterokaryon of Neurospora crassa, collected on Millipore filters or in suspension, were flown aboard the Gemini-XI spacecraft to permit an evaluation of the genetic effects of radiation in combination with spaceflight parameters such as "weightlessness." A ground-base experiment was performed simultaneously as the control. The samples were exposed to different amounts of32 P β-irradiation, and the survival levels and forward-mutation frequencies in the ad-3 region studied. Analysis of survival and forward-mutation frequency has been completed; characterization of the ad-3 mutants is in progress. The results show that in-flight and ground samples irradiated on filters do not differ significantly either in survival levels or forward-mutation frequencies, confirming the finding of the Gemini-XI blood experiment that no synergism exists between radiation and spaceflight parameters. Significant differences were found among samples irradiated in suspension, however....