Fertilization process

Haploid nucleus from a sperm fuses with haploid nucleus of an egg cell. Only one sperm fertilizes the egg. As the head of the sperm enters the egg, it triggers off the formation of an extra cell membrane around the egg. This stops any sperm entering the egg. The sperm's tail is left outside the egg. The head contains a nucleus and this fuses with the egg's nucleus. Both are haploid(23 chromosomes). After fertilization, a diploid zygote is formed(46 chromosomes).