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MEIOSIS PowerPoint Presentation

MEIOSIS

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MEIOSIS

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Presentation Transcript

  1. (the formation of sex cells) MEIOSIS

  2. Purpose of Meiosis The purpose of meiosis is to produce gametes or sex cells (sperm and egg cells) with half the number of chromosomes as the original cell. In humans, each gamete contains only 23 chromosomes. This ensures that when sperm and egg cells combine the resulting cell (a zygote) will have the same number of chromosomes as the original cell (46 chromosomes).

  3. Overview of Meiosis • During meiosis cells divide twice, unlike mitosis where there is only one cell division. • As a result, 4 cells are produced instead of 2. MitosisMeiosis However, the process of meiosis is different in males and females.

  4. Spermatogenesis(the formation of sperm cells) • In males, meiosis takes place in the testes • Each of the four haploid cells produced develop into sperm cells • Healthy men can produce sperm from puberty until the day they die. Pierre Elliot Trudeau, former Prime Minister of Canada fathered a child when he was 72 years old!

  5. Oogenesis(theformation of egg cells) • In females, meiosis takes place in the ovaries • Each time the cells split the cytoplasm is divided unevenly • This results in one large cell and three tiny cells (polar bodies) • Only the large cell survives and becomes an egg cell Unlike men, women are born with all of the egg cells they will ever have! They release one egg a month (on average) during menstruation. When all of their eggs are gone they enter menopause.

  6. Comparing Mitosis and Meiosis