Segregation of univalents on mini spindles.

Abstract

MANY authors have reported that the behaviour of univalent chromosomes at meiosis is irregular. At metaphase they tend to lie off the metaphase plate and closer to the poles than the bivalents; and it has been suggested that this is because the univalents move to the poles earlier. In the triploid species Leucopogon juniperinus univalents are close to the poles at metaphase, but serial sections show that they are not in the same plane as the spindle on which the bivalents are positioned (Fig. 1). Closer examination of the metaphase cells shows that the univalents are attached to a separate, much reduced spindle, which is attached to the same pole as the “bivalent” spindle but is formed in a different plane (Fig. 1, cells 2 and 3).