in this 8-cell embryo called the memorial a for its barry like appearance old cells express a pair of jeans cdx2 and oct 3/4 but as the cells at the memorial through their next round division cdx2 is downnregulated in the intermost selves well Oct 3-4 remains expressed throughout the segregation in these jeans is maintained as the cellscontinue to dividein till after about 10 rounds a division the embryo has become a hollow ball known as a blast assist the outer layer above last assessed is made up entrely of cells that express cdx2