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. Levels of survival were higher and frequencies of forward mutation lower in the in-flight samples than in the ground samples. Since these differences do not agree with data from our other tests, they may have been the result of anoxia caused by high temperatures in the spacecraft cabin, instead of protection against the genetic effects of radiation by weightlessness.

This content is only available as a PDF.
You do not currently have access to this content.