meiosis

a type of CELLS division that occurs in the maturation process of the GAMETES (sperm and ova) so that the sex cells eventually contain only half the number of CHROMOSOMES of the parent cells from which they are derived. The daughter cells also have genetic variation from the parent cell, brought about by a process known as 'crossing over', which occurs during meiosis. When sperm and ovum fuse at FERTILIZATION , the full chromosome number is restored in a unique combination in the EMBRYO . There are two phases of division in meiosis each of which is divided into four stages, namely prophase, metaphase, anaphase and telophase.