with the fast block to polyspermy the calcium "activates" the cell, substantially increasing metabolism.
             Another effect of the fusion of gametes is the cortical reaction, where calcium is released into the cytosol. Cortical granules, lying under the plasma membrane, sense the calcium increase and release their contents to form the fertilization membrane, which resists the entry of other sperm. This functions as the slow block to polyspermy to serve after the fast block has ended.
             Fingerlike extensions of the mammalian egg cell, microvilli, take the entire sperm into the egg. The basal body of the sperm's flagellum divides and forms two coatrooms in the zygote. These will generate the mitotic spindle for cell division. The nuclei of the sperm and egg do not immediately fuse as they do in non-mammals, instead the envelopes of both nuclei disperse and the chromosomes from the two share a common spindle apparatus during the first mitotic cell division; thusly forming a diploid cell.
             Following fertilization a process called cleavage creates a multicultural embryo. During cleavage the cells undergo DNA synthesis and mitosis phases of the cell cycle but usually skip the G1 and G2 phases. The embryo does not enlarge during cleavage, it simply divides the single large zygote into many smaller cells called blastomeres each with its own nucleus.
             With the exception of mammals, most eggs of animals have a distinct polarity divided into a vegetal pole (having most amount of yolk) and animal (having least amount of yolk). Yolk is the nutrients stored in the egg. The polarity effects the speed of the division. Continu
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