Repair of Genetic Radiation Damage - A Possible Cause of Differential Radiosensitivity in Drosophila Melanogaster

The extent to which differential radiosensitivity in gametogenesis of Drosophila melanongaster can be explained by metabolic repair of premutational damage (including the rejoining of radiation-induced chromsomes breaks) la discussed in thia paper. Three stager of gametogenesis are considered, in which repair might occur: (1) late spermatids (''immature sperm''); (2) the gonial stage (both of spermatogenesis and oogenesis); and (3) prophase I - oocytes. Experimental proof is given that there is no repair by storing of mature sperm. An hypothesis is proposed to explain the striking differences observed for the dosage-effect-relationships for dominant lethal induction in metaphase I (''Sage 14'') and prophase I (''Stage 7'') oocytes, respectively. This hypothesis is partly based on differential repair (restitution) of chromatid breaks in these two oocytic stages. The implications of the low radio- sensitivity of gonia and early oocytes for radiation damage to human germ cells are briefly considered. (author)