An analysis of the mutability of developmental stages of male gametes of the japanese quail (Coturnix coturnix japonica), after irradiation with /sup 60/Co exposures (5.16; 15.48; and 30.96)x10/sup -2/C kg/sup -1/, i.e. 200, 600 and 1200 R, at an exposure rate of 8.59x10/sup -5/C kg/sup -1/s/sup -1/, i.e. O.33 R s/sup -1/, has shown that the rate of overall induced dominant lethality as well as the rate of mutation were highest in spermatocytes of the second order at all exposures. Starting from an exposure of 200 R the following values were found for lethal interference per 1 gamete for 1 R: spermatozoa 2.0x10/sup -3/, spermatides 1.95x10/sup -3/, spermatocytes II 6.1x10/sup -3/, spermatocytes I 4.06x10/sup -3/, spermatogonia in the process of differentiation 6.8x10/sup -3/. When analysing overall embryonic lethality, according to early and late lethality, dominant lethal mutations mainly manifested themsel--ves in the oviductal and germinal developmental periods, so that these periods can be considered as sensitive indices of genetic changes. The spermatogenic epithelium of the japanese quail was found to be greatly radioresistant since not even an exposure to 1200 R caused complete and permanent sterility.
Baumgartner, J 
- Vyskumny Ustav Chovu a Slachtenia Hydiny, Laboratorim Genetiky, Ivanka pri Dunaji (Czechoslovakia)