Question 89

(Multiple Choice)

In humans, identical twins are possible because


A) cytoplasmic determinants are distributed unevenly in unfertilized eggs.
B) extraembryonic cells interact with the zygote nucleus.
C) convergent extension occurs.
D) early blastomeres can form a complete embryo if isolated.
E) the gray crescent divides the dorsal-ventral axis into new cells.

Answer