PRINCIPAL INVESTIGATOR (S ): Frederick J. deSerres 



EXPERIMENT TITLE/NUMBER : Mutagenic Effectiveness of Known Doses of Radiation 



in Combination with Zero Gravity on Neurospora 

 crassa . P-1037 



PROGRAM/MISSION : Biosatellite II 



CLASSIFICATION : Microorganism - ( Neurospora crassa ) 



DISCIPLINE (S) : Radiobiology, Genetics, Cell biology 



OBJECTIVES : To study the genetic effects of spaceflight alone and in 

 combination with known doses of radiation. 



PROTOCOL : A genetically marked two-component 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 dose-response curves. 



EQUIPMENT : Millipore filters, LiF disk dosimeter, porous retaining rings 

 (sample holder), module of sample holders, Sr source, thermistor. 



RESULTS : There was no difference between the flight and Earth control samples 

 for survival, the overall induction of ad- 3 mutations, or for point mutations 

 or chromosome deletions. 



CONCLUSIONS : The effects of weightlessness on radiation-induced genetic 

 damage are complex. Both antagonistic and synergistic effects of radiation 

 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. 



PUBLICATIONS : 145, 1Mb, 147, 148, 150, 151, 152, 153 



160 



