Figure 3. Distribution of
pos-1 gene products. Each row compares two embryos at a comparable stage. The left column shows brightfield images of embryos after in situ hybridization for
pos-1 mRNA (darkly staining regions), and the right column shows immunofluorescence micrographs of embryos after staining with POS-1 antiserum (white regions). Embryos are oriented as in Fig. 1. (A,B) Newly fertilized, precleavage egg; (C,D) 2-cell stage; (E,F) early 4-cell stage, double-headed arrow in F indicates the sister blastomeres EMS and P2; (G,H) late 4-cell stage; (I,J) 15-cell stage;(K,L) approximately 28-cell stage. (M,N) Embryos midway through embryonic development after the division of P4.