Question

Mention the event that induces the completion of the meiotic division of the secondary oocyte.

Answer 1

Usually 23 chromosomes from spermatozoon and 23 chromosomes from egg cell fuse (half of the spermatozoon carry an X chromosome and the other half Y chromosome[14]). Their membranes dissolve, leaving no barriers between the male and female chromosomes. During this dissolution, a mitotic spindle forms between them. The spindle captures the chromosomes before they disperse in the egg cytoplasm. Upon subsequently undergoing mitosis (which includes pulling of chromatids towards centrioles in anaphase) the cell gathers genetic material from the male and female together. Thus, the first mitosis of the union of sperm and oocyte is the actual fusion of their chromosomes.

Each of the two daughter cells resulting from that mitosis has one replica of each chromatid that was replicated in the previous stage. Thus, they are genetically identical.