Lack of Cyclin B1 in zebrafish causes lengthening of G2 and M phases.

An essential part of the Mitosis Promoting Factor, Cyclin B1 is indispensable for cells to enter mitosis. We report here that the zebrafish early arrest mutant specter is a loss-of-function mutation in the сyclin B1 gene. cyclin B1 is maternally transcribed in zebrafish, and the zygotic phenotype is apparent by early segmentation.