Genetic control of DNA replication in chromosomes of eukaryotes.

It has been found that the formation of multinuclear polyploid cells in plants due to colchicine action results in the "lysis" of some nuclei formed.The nuclei lacking the chromosome possessing the nuclear organizer (N. O.) are subject to lysis.In Haplopappus gracilis, for example, whose genome consists only of two pairs of chromosomes (2n = 4), tetraploid nuclei having four chromosomes without the nuclear organizer are lyzed. At the same time in the extra nucleus of the cell, with one pair of chromosomes possessing the nuclear organizer, these chromosomes undergo the next reproduction.In experiments with H(3)-labelled thymidine, DNA synthesis is blocked in the nuclei having no nuclear organizer.The data obtained suggest a hypothesis concerning the control mechanism of DNA synthesis and chromosome replication in eukaryotes.