Where do babies come from?

Babies come from the fertilization of a female’s egg with a male’s sperm. Conception occurs after the ovulation of a female’s egg and ejaculation of a male’s sperm. Eggs and sperm are called gametes, or sex cells. Each gamete contains the haploid number (n) of chromosomes. Fertilization is the union of an egg and sperm. Upon contact with an egg, a sperm produces enzymes that allow it to penetrate the jelly coat of the egg cell. The union of egg and sperm chromosomes reestablishes the diploid number (2n) of chromosomes for a species. This fertilized egg is called a zygote. The zygote contains all the genetic information required to make an individual. The zygote then begins to undergo mitosis. Initially, all cells are the same. As the embryo begins to grow, specialization of cells occurs. Differentiation of stem cells is due to which parts of the DNA are activated. Eventually, a fetus is developed within the mother’s uterus. After full term, the mother gives birth.