Objectives:An experiment exploring the mutagenic effects of known doses of radiation in combination with microgravity on Neurospora crassa was first flown on the Gemini XI mission, in 1966. In Gemini XI, conidia were tested on both the surface of Millipore filters and in a colloidal suspension of sugar, and a 32P beta- ray radiation source was used. This experiment was to conduct a similar study on the genetic effects of space flight alone and in combination with known doses of radiation, on the surface of Millipore filters, using a 32Sr gamma-ray radiation source.
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Approach:
A genetically marked two-compartment heterokaryon, heterozygous for two different genes that control sequential steps in purine biosynthesis, was used. The frequency of radiation-induced recessive lethal mutations, chromosome deletions, and overall survival were studied. A range of radiation exposures was given to determine the dose-response curves.
Results:
There was no difference between flight and ground control samples for survival, the overall induction of ad-3 mutations, or for point mutations or chromosome deletions. Gemini XI data show that space flight affected samples on Millipore filters in the same way as on Biosatellite II, with no effect on survival or mutation induction. Gemini Neurospora flown in suspension, however, had higher levels of survival and lower frequencies of mutation induction, due to a specific effect on point mutations and not on chromosome-deletion mutations. Through addition postflight experimentation, it was shown that anoxia, which may have occurred inflight, can produce a reduction in the frequencies of both point-mutations and chromosome-deletions. The effects of weightlessness on radiation-induced genetic damage are complex. Both antagonistic and synergistic effects have been found. The results depend on the assay system; in most cases however, the effects are small, twofold to fivefold differences being the usual order of magnitude.
de Serres, F.J. and B.B. Webber: Genetic Effects of 85Sr Irradiation on Neurospora crassa. Radiation Research, vol. 35, 1968, pp. 436-444.
de Serres, F.J. and B.B. Webber: Mutagenic Effectiveness of Known Doses of Radiation in Combination with Zero Gravity on Neurospora. BIOSPEX: Biological Space Experiments, NASA TM-58217, 1979, p. 160.
de Serres, F.J. and B.B. Webber: The Induction of Recessive Lethal Mutations Under Weightlessness in the Neurospora Experiment on the Biosatellite II Mission. Radiation Research, vol. 43, 1970, pp. 452-459.
de Serres, F.J.: Effects of Radiation During Spaceflight on Microorganisms and Plants on the Biosatellite II and Gemini 11 Missions. Life Sciences and Space Research: Proceedings of the 11th Plenary Meeting, Tokyo, Japan, May 14-16, 1968, North Holland Publishing, 1969, pp. 62-66.
de Serres, F.J.: Effects of Weightlessness on Simple Life Forms in Biosatellite II. Federation of American Society for Experimental Biology, 56th Annual Meeting, Atlantic City, N.J., April 9, 1972, Conf-720441, 1972, p. 8.
de Serres, F.J.: Effects of Weightlessness on Simple Life Forms in Biosatellite II. The Physiologist, vol. 16, 1973, pp. 225-228.
de Serres, F.J.: Mutagenic Effectiveness of Known Doses of Radiation in Combination with Zero Gravity on Neurospora crassa. The Experiments of Biosatellite II, NASA SP-204, 1971, pp. 325-331.
de Serres, F.J.: Neurospora Experiment P-1037. Final Report, NASA CR-112355, 1970.
Saunders, J.F. et al.: The Experiments of Biosatellite II. S.A. Gordon and M.J. Cohen, eds., Gravity and the Organism, University of Chicago Press, 1971, pp. 443-450.
