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DNA Replication in Chrysanthemum lineare, Ch. nipponicum and their F1 Hybrid

1966; Botanical Society of Japan; Volume: 79; Issue: 939 Linguagem: Inglês

10.15281/jplantres1887.79.447

2185-3835

田中 隆荘,

Photosynthetic Processes and Mechanisms

In the present investigation a comparative H3-thymidine autoradiography was made on the chromosome size difference between Chrysanthemum lineage (2n=18) and Ch. nipponicum (2n=18). The duration of phases in the mitotic cycle was measured. The DNA replicating pattern in the chromosomes was also analyzed.1. The chromosomes of the two species synthesized DNA in similar duration (about 10hrs.) and showed similar duration in mitotic cycles (about 15hrs.).2. In the F1 hybrid the chromosomes of the two species replicated in synchrony.3. Differences were found between Ch. Lineage and Ch. nipponicum concerning late DNA replicating regions, DNA replication in satellites and the number of DNA replicating positions: Most of the chromosomes of Ch. lineage had late DNA replicators in the proximal regions, while most of the chromosomes of Ch. nipponicum had late DNA replicators in the distal regions. The satellites of the three chromosomes of Ch. lineage were middle replicators, while the satellites in the chromosomes of Ch. nipponicum were found to be late replicators. At all stages in the DNA synthetic phase the chromosomes of Ch. lineage showed approximately twice as much labelling as the chromosomes of Ch. nipponicum, indicating greater number of DNA replicating positions in the former than in the latter.4. Considerations were given to the relationship between morphologically different heterochromatic regions and the late replicators, as well as to the relationship of chromosome size to DNA replicating units.