Visualization of the interphase chromosomes of Ornithogalum virens and Muntiacus muntjak

A technique for visualizing "interphase chromosomes" was applied to nuclei of the angio-spermous plant, Ornithogalum virens (2 n = 6), and the male mammal, Muntiacus munjak (2 n = 7), in an attempt to correlate the numbers of "chromosomes" visible during interphase with the respective diploid chromosome numbers. The alterations in chromosome structure observed during G1, S, and G2 periods were comparable to those previously reported in Allium cepa and Chinese hamster (CHO line) cells [33], but for technical reasons it was only possible to make accurate counts of interphase chromosomes in the G1 nuclei of O. virens. In addition, from our observations of interphase chromosomes that were pulse-labelled with tritiated thymidine and a parallel study of premature chromosome condensation (PCC) using pulse-labelled M.muntjak cells, we conclude that, although chromatin decondensation may be required for DNA synthesis, extreme chromatin decondensation can occur in the absence of DNA synthesis. Generally a morphological description of alterations in chromatin during interphase only roughly parallels the G1, S, and G2 phases defined by autoradiography following incorporation of tritiated thymidine. We suggest that both methods are valid through different ways of describing interphase.