Fig. 3. P cell lineages in pag-3 mutants. Abnormalities in pag-3 lineages are indicated by bold lines; surviving cells that die in wild-type lineages are indicated by circles. Cells that die in wild-type animals are indicated by an x; additional cell deaths observed in pag-3 mutants are indicated by an underlined x. pag-3 mutants initiated P cell divisions at the same time during development as wild-type animals. The time scale in B applies to all lineages. (A) Lineages of wild-type animals from Sulston and Horvitz (Sulston and Horvitz, 1977). (B) Lineages of pag-3(n3098) mutants. (C) P9-P12 cell lineages of three pag-3(ls20) mutants. The variability we observed in the division patterns and cell fates in pag-3 mutants has been observed generally in mutants with cell lineage defects (Sternberg and Horvitz, 1984). In reiterated divisions, the time between mitoses became progressively longer and the morphology during mitosis more abnormal with each round of reiteration, often with what appeared to be aborted attempts at cell division. In those lineages in which the posterior daughter would normally have undergone programmed cell death, cell death often occurred later than observed in wild-type lineages and sometimes did not occur. (D) The cell fates in P cell lineages of wild-type and pag-3 mutant animals. A,B,C,D,E are distinct cell fates, representing cells that may divide, survive and differentiate, or undergo programmed cell death. VA, VB and VC are motoneuron classes (White et al., 1976). ‘Pn.aa’ is a neuroblast that divides to generate daughter cells like those normally generated by Pn.aa. (E) Experimentally determined cell fates in the Pn.a lineages of wild-type (Sulston and Horvitz, 1977; White et al., 1976; White et al., 1986) and pag-3 mutant animals. Cell fates were assessed as described in the text. ±VA is an abnormal VA cell (see text). The fate of the presumptive DAS cell in pag-3 mutants was not tested experimentally (DAS).