Fig. 5. Analysis of division orientation.

Analysis of division orientation at the 4^th and 5^th cleavage divisions. (A) Percentage of asymmetric and symmetric divisions in 4^th and 5^th cleavage (average ± SEM). (B) Analysis of cell division orientations of the two daughters of an asymmetric (A) or symmetric (S) division in the 4^th cleavage round. The possible permutations (shown) differ significantly depending on the orientation of the 4^th cleavage (χ² test, p<0.001). ‘I’ denotes a division where both daughters lie inside the embryo. (C,D) Proportion of asymmetric/symmetric divisions of the 4-cell-stage descendants at 4^th and 5^th cleavage (average ± SEM) for the four classes. (C) ME and EM embryos, (D) MM and EE embryos. Each pair of columns represents the descendants of one of the 4-cell blastomeres (legend of Fig. 2 for abbreviations).