The creation of a chimeric mammalian embryo illustrates some

The creation of a chimeric mammalian embryo illustrates some unique features of mammalian development. How does compaction affect the experimental procedure for making a chimera? What do you think would happen if you took 8 cells from each of 3 8-cell embryos and combined them? Alternatively, what do you think would happen if you took 2 cells from each of 3 8-cell embryos and combined them?

Solution

The chimera embryo consisting of 8 loosely associated and nonpolar blastomeres.In this stage the embryo has transcribed and translated most of the proteins required for cell differentiation and polarity.This switch in blastomere from nonpolar to polar at 8 cell stage results from cell cell adhesion.This is called Compaction. Here each of the eight blastomeres interacts with its neighbors to undergo membrane polarization.

Different components of the cell surface migrate to different regions of the cell.

this cell polarity marks the initiation of trophectoderm differentiation.

Now division of 8 polarized blastomeres results in the formation of 2 distict phenotypes in 16 cell morulla

The inner cell mass will give rise to the embryo proper, the yolk sac and allantois, while the fetal part of the placenta will form from the outer trophoblast layer.

We know that Compaction appears first at 8 celled stage.

2. If we take 2 cells from 3 - 8 celled embryo and combined them then 6 cell mass will form.So this cell mass