Question

How do the cells in a blastocyst change as it becomes an embryo

Answer 1

1. Passage of a sperm through the corona radiata of the oocyte.
2. Penetration of the zona pellucida.
3.Fusion of the plasma cell membranes of the oocyte and sperm. after fusion the sperm head and tail enters the oocyte but plasma membrane of sperm doesn't.
4. Completion of the second meiotic division of the oocyte. this creates female pronucleus and polar body 2.
5. Formation of the male pronucleus (nucleus of sperm enlarges)
6. Breakdown of the pronuclear membranes and restoration of diploid number of chromosomes.