 After fertilization, events are already occurring in the zygote to allow for the first asymmetric cell division.This first division produces two distinctly different blastomeres, termed AB and P1.When the sperm cell fertilizes the egg cell, the sperm pronucleus and centrosomes are deposited within the egg, which causes a cytoplasmic flux resulting in the movement of the pronucleus and centrosomes towards one pole.