The durations and compositions of cell cycles in leech, Helobdella triserialis

Abstract

When tritiated thymidine triphosphate ([3H]TTP) or its immunohistochemically detectable analogue, triphosphate (BrdUTP), is injected into blastomeres of passes throughout the entire embryo and is rapidly 2min after injection) into nuclei of cells In the same embryos a DNA-specific stain can be used in mitosis (M phase) or nonreplicative interphase (G1 the basis of nuclear or chromosomal morphology. Using we have determined the lengths and compositions of the cycles of identifiable cells in early embryos of the triserialis, and have analysed how the cell cycles first seven stages of development. The relatively the early blastomeres comprise not only phases of M postreplicative gap (G2) phases. The lengthening of that occurs as development progresses is primarily increase in the length of G2 and secondarily by an length of S and, in some instances, the addition of a gap (G1) phase; M phase remains relatively constant. that the durations of the cell cycles of embryonic by a variety of mechanisms.