Fig. 3. Model for the generation of blastocyst pattern. The 32-cell mouse embryo consists of two clones derived from 2-cell blastomeres, which show an arrangement reminiscent of a `baseball'. Based on the arrangement of 2-cell-stage clones, there are three different possibilities for the positioning of the blastocyst cavity (white dot). (A) The cavity develops within one clone which leads to embryonic/abembryonic pattern. (B) The cavity forms over the border between the 2-cell-stage clones which leads to `half-half' pattern. (C) The cavity forms more randomly with respect to the border of the 2-cell clones generating blastocysts with `mixed' pattern. (D) Scheme illustrating the lineage-dependency of the different patterns. Only the embryonic-abembryonic pattern reflects the lineage history with respect to the 2-cell stage.