Autoradiographic studies on the incorporation of3H-amino acids into chromosomes during the mitotic cell cycle ofHaplopappus gracilis |
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Authors: | Yoshihiko Yonezawa Ryuso Tanaka |
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Institution: | (1) Botanical Institute, Faculty of Science, Hiroshima University, 730 Hiroshima |
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Abstract: | The synthesis of chromosomal proteins and the incorporation of labelled proteins into chromosomes in the mitotic cell cycle
ofHaplopappus gracilis, 2n=4, were traced autoradiographically with3H-arginine,3H-lysine, and3H-tryptophane. The duration of the mitotic cell cycle in the root tip cells was determined by3H-thymidine autoradiography and was measured to be 13.0 hr (G1 1.3 hr, S 6.5 hr, G2 3.8 hr and M 1.4 hr).3H-arginine labelled proteins which were synthesized at S and G2 were found to be incorporated into chromosomes to a greater extent than proteins which were synthesized either at G1, at the transition phase from late S to early G2, or at the mitotic phase. Such varied incorporation was also found in3H-lysine labelled proteins, but not in3H-tryptophane labelled proteins. These findings indicate that the chromosomal proteins are synthesized mainly at S and G2. Some of the3H-arginine labelled proteins which were synthesized during the first mitotic cell cycle, were found to be incorporated into
the chromosomes of the second mitotic cell cycle. The incorporation of the proteins synthesized at one stage of the mitotic
cell cycle was found to occur locally in some regions of the chromosomes, while the pattern of incorporation was observed
to be similar between euchromatic and heterochromatic regions. |
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