試題詳解

24. In humans, identical twins are possible because
(A) of interactions between extraembiyonic cells and the zygote nucleus.
(B) of the heterozygeneous distribution of cytoplasmic determinants in unfertilized eggs.
(C) the gray crescent divides the dorsal-ventral axis into new cells.
(D) of convergent extension.
(E) the blastomeres are genetically the same.