| Abstract: | The time of action of the genes controlling the decrease of aldolase activity (21-23 hrs of development) and its subsequent increase (23-36 hrs) was determined by means of inactivation of the nuclei by actinomycin or heavy doses of irradiation at succesive developmental stages. There exist two distinct periods of gene activity; the former (15-18 hrs) determines the rapid fall of maternal aldolase activity and the latter (21-27 hrs) its subsequent replacement by embryonic aldolase. This result is confirmed by the data concerning the changes in aldolase heat resistance in the hybrids of the loach and tropical cyprinids. The genes controlling the synthesis of the new aldolase and the morphogenesis which takes place at the same developmental stages are functioning at different times, i.e. the biochemical and morphological differentiations may occur relatively independently. |
