In meiosis II, the homologs are separated into individual chromatids which are then placed into separate cells after cytokinesis.

In meiosis I, the homologous chromosomes are separated from one another and placed into separate cells after cytokinesis. The first meiotic division is called MEIOSIS I and the second is called MEIOSIS II. The second meiotic cell division involves another nuclear division and another cytokinesis. The first meiotic cell division involves a nuclear division and then a cytokinesis (cytoplasm division). That is why meiosis occurs in two stages or divisions. Meiosis cannot split a 2N nucleus into a 1N nucleus in a single division. Since sperms and eggs contain only the 1N (haploid) number of chromosomes they can safely fuse (sperm with egg), and produce a fertilized egg with the correct number of chromosomes that can then develop normally. If they do not fuse (sperm with egg) they will die. Because of this, sperms and eggs will not survive for long. Meiosis splits the nucleus so that the daughter cells have one-half the normal number of chromosomes - the haploid number. All sperms and eggs are made by MEIOSIS AND CYTOKINESIS. The nucleus is not split by mitosis as in normal cell division. Sperms and eggs are produced by a unique cell division process. The fertilized egg would have twice the amount of genetic material it must have. If a 2N (diploid) sperm united with a 2N egg, the results would be disastrous (4N). Since mitosis produces daughter cells with the diploid number of chromatids, it cannot be used for sperm or egg production. Since gametes must fuse, they must each have one-half the normal number of chromosomes so that when they fuse they have exactly the right amount. Gametes cannot be made by normal cell division. Normal cell division is used by unicellular organisms for reproduction, and in multicellular organisms for growth, maintenance, and repair. Sperms and eggs are haploid cells.Ĭells are usually created by normal cell division involving mitosis and cytokinesis.

Some cells do not have chromosomes in pairs but rather singly, or as individuals - one of each. Sperms are produced in TESTES, organs usually located outside the lower abdominal region of mammalian males.Ĭhromosomes usually exist in pairs in sexually reproducing organisms and for this reason most sexually reproducing organisms are termed DIPLOID ( 2N) because they have chromosomes in pairs. Eggs are produced in OVARIES, an organ located in the lower abdominal region of all mammalian females. Gametes are produced in special organs only. No ordinary cell (skin or bone) is capable of such a feat. They are unique in that they (sperm and egg) contain the developmental potential to produce an entire organism composed of trillions of cells. Males of a species produce sperm - cells that can swim to another cell, and females produce eggs - cells that contain all of the nutrients to start a new organism. The fusion cells are called GAMETES, or sex cells.

Sexual reproduction involves the fusion of two living cells which will then grow into a new offspring. Sexual reproduction is more successful because the offspring have more genetic variety, getting DNA from 2 sources instead of 1. Most organisms sexually reproduce - meaning that they use another organism to produce an offspring. This method of reproduction is not very successful and most organisms on earth do not reproduce this way. (To fully understand this program, you must have completed the program of MITOSIS, go there if you have not done so already.)Ī simpler way to reproduce is through asexual reproduction, where one organism produces an offspring by itself. Most life forms on earth sexually reproduce - that is they fuse sex cells to make offspring. All life forms are able to reproduce only because their cells that make them up are capable of this feature. One of the fundamental and truly unique characteristics of all organisms is their ability to reproduce.

Prophase ii