Blastomere In Situ Hybridization AntibodyAn antibody is formed to bind to a particular gene product. LabelThe antibody is labeled so it is easily visible when bound to its antigen. 2-8 CellsUntil the 2-8 cell stage, gene expression is consistent in all cells. LaterAfter the 2-8 cell stage, gene expression begins to vary from cell to cell. ConclusionLoss of totipotency is due to differential gene expression. All cells remain genomically equivalent, though different genes become activated in different cells.