The detached Calcium N5-methyltetrahydrofolate chromatid was located between the separating anaphase chromosomes and may be merotelically attached to the spindle. Unexpectedly, detached chromatids were also located at position closer to the spindle pole than the chromosomes or at the side of the chromosomes, Pembrolizumab possibly reflecting syntelical or monotelical attachment to the spindle. Chromatids located in these positions produced micronuclei. This chromatid is not the ����lagging chromatid���� in a strict sense, however, we will use this term for all detached chromatids as this term is commonly used for micronuclei formation. The chromatin bridge and the lagging chromatid might simultaneously appear in the same mitotic cell and they can independently generate micronuclei. By examining many time-lapse movies captured during the initial 72 hours in the presence of HU, we observed on 212 occasions micronuclei generation just after mitosis. As shown in Fig. 3G, 37% and 63% of the micronuclei were generated from the bridge and the lagging chromatid, respectively, under these conditions. A part of the chromatin bridge might remain as the nuclear bud after its resolution. Such a mechanism would explain 29% of the buds that were detected just after mitosis. On the other hand, the buds might also appear at the end of mitosis in the absence of detectable chromatin bridges. This type of bud constituted 28% of the total buds. Furthermore, there were buds that were generated long after the apparently normal mitosis, typically by the protrusion of the interphase nucleus. This type of bud constituted 43% of all buds. There were also nuclear buds that appeared to be converted to micronuclei. The frequency of such events was quite low under these conditions and is not depicted in Fig. 3G. Under HU-induced replication stress, multipolar mitosis occurred frequently. It was suggested that HU might result in the over-replication of the centriole by inducing DNA damage and uncoupling the centriole cycle and the cell cycle. Such multipolar mitosis frequently generated the chromatin bridge and/ or the lagging chromatid, which resulted in micronuclei formation. The representative time-lapse images for the generation of bridge or lagging chromatid from tripolar mitosis is shown in Fig. 2A and B, and their frequency among the 349 dipolar or 57 multipolar mitoses are summarized in Fig. 4C.