FATE OF MATERNAL MTDNA FOLLOWING CO-60 INACTIVATION OF MATERNAL NUCLEAR-DNA IN UNFERTILIZED SALMONID EGGS

The effects of gamma irradiation on nuclear DNA and mitochondrial DNA (mtDNA) were examined by exposing unfertilized salmonid eggs to a Co-6 0 Source. Brown trout (Salmo trutta) eggs exposed to Co-60 were fertil ized with sperm from brook trout (Salvelinus fontinalis), and brook tr out eggs exposed to Co-60 were fertilized with sperm from splake males (S. namaycush X S. fontinalis). In both types of matings only paterna l allozymes were found in embryos, confirming the inactivation of the nuclear genome in the eggs. Analysis of mtDNA in these same embryos sh owed exclusively maternal mtDNA. The absence of paternal mtDNA among a ny of the embryos supports the predominance of maternal inheritance of mtDNA in vertebrates and suggests that mtDNAs are more resistant to c obalt inactivation than nuclear DNAs based on structure or numerical s uperiority to maternal nuclear DNA. Inactivation of maternal nuclear D NA, fertilization, and an induced return to the diploid state provide a means for producing an inbred organism having the nuclear genome of the paternal parent (androgenetic) and the mitochondrial genome of the female.