RNA SYNTHETIC ACTIVITY IN THE MITOTIC NUCLEI

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RNA synthesis during mitosis was studied by autoradiographic techniques in the root meristematic cells of Luzula purpurea (n=3).
Comparisons of the synthetic activity of the interphase with those of other mitotic phases were made using whole nuclear grain counts.
Incorporation of uridine-H³ in chromosomes decreased during early-prophase and completely stopped at mid-prophase. Incorporation of uridine-H³ in nucleoli was retained until late-prophase, just before nucleolar disintegration. No incorporation of uridine-H³ was observed in meta-anaphase chromosomes. Incorporation of uridine-H³ into the daughter chromosomal groups began at early-telophase and continued until late-telophase.
Pre-nucleolar material appeared on the surface of each chromosome as early as in late-anaphase before RNA synthesis resumed in daughter nuclei. Nucleolus developed in parallel with an increase of the incorporation of uridine-H³ in chromosomes and nucleolus itself.