Chromosome aberrations and the mitotic cycle in trillium root tips after x-irradiation

An effect of fixation and staining on the realization of cold-induced heterochromatin in Trillium

“…Although this experiment was timed to show labelled X2 cells in division, in practice the considerable degree of asynchrony between cell populations (Grant, 1965) allows a comparison of three different types of cell: those which were not in S at the time of labelling (67 per cent, of the total mitoses); the fully labelled cells that are in their first (X1) division since labelling (i8 per cent. ); and the half-labelled cells in X2 (15 per cent.).…”

“…In this study two plants were used from a clone of Trillium grandifiorum of which a photograph of the chromosomes after cold treatment is given in Grant (1965).…”

“…3H-thymidine (specific activity '8 C/mM) for 12 hours at 25°. They were then grown for 6 days at 25° to allow the labelled cells to divide once, to complete a second DNA replication in the absence of label, and to enter the G2 preceding the X, division (at this temperature one mitotic cycle takes about 5 days, for other data see Grant, 1965). At this stage the roots were cooled to 2 '5° and after 5 more days they were separated into two groups of 5.…”

“…ROOT tips of Trillium species continue to synthesise DNA between o° and 30 (Boothroyd and Lima de Faria, 1964;Grant, 1964) and replication of the heterochromatin is completed at the same time as that of the euchromatin (Grant, 1965). But studies of the first (X1) mitosis indicate that the H-segments which are labelled with 3H-thymidine at ordinary temperatures apparently lose this label if they are cooled to o° after their entry in the G2 phase (Haque, 1963;Grant, 1964).…”

Reassociation patterns among segmental interchanges in maize

“…Thus, it appears that there are sufficient reports of species (Grant, 1965) and cytogenetic differences (e.g. Kaufmann, 1946;Michaelis and Rieger, 1968;Morad et al, 1973) to discount most generalisations which attempt to comment on specific units of a chromosome.…”