エゾミズゼニゴケ雄株における異質染色質の早期 DNA 合成とY染色体の複製について

Abstract

DNA synthesis of the heterochromatin of Y-chromosome in malePellia neesiana (Gottsche) Limpricht, Hepaticae, was investigated by treating its thalli with 20 μc/ml H3-thymidine.The first appearance of the activated silver grains on the interphase nuclei was observed at 2 hour and that on the mitotic chromosomes at 8 hour from the beginning of H3-thymidine treatment. Y in the mitotic nuclei fixed at 8 hour were observed to have grains only at the euchromatic segment, while the heterochromatic segments had no grain. Labelling of the heterochromatic segments in Y was observed for the first time in the mitotic nuclei fixed at 10 hour. In these nuclei there were no difference of grain density between the heterochromatic segments and the euchromatic segment. In the mitotic nuclei fixed at 22 hour the heterochromatic segments in Y were observed to have more grains than its euchromatic segment. These results show that the heterochromatins of Y synthesize its DNA earlier than the euchromatins of Y and autosomes.Observations on the autoradiographs of the heteropycnotic bodies at interphase nuclei confirmed that DNA in the heterochromatin of Y is replicated in the diffused state.