Why are human sex cells haploid? Why do they contain 23 chromosomes?
Meiosis occurs in humans and other kinds of organisms. When it occurs in humans, each diploid cell that undergoes meiosis contains 46 chromosomes (44 autosomes + 2 sex chromosomes). As a result of meiosis, four haploid daughter cells are formed, the sex cells, each with 23 chromosomes (22 autosomes + 1 sex chromosomes). Therefore, at fertilization, the haploid (23N) nucleus of the sperm and and the haploid (23N) nucleus of the egg fuse to form a diploid (46N) zygote (which is a fertilized egg that will eventually develop into a baby, if all goes well).