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MEIOSIS NOTES (11.4)

MEIOSIS NOTES (11.4)

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MEIOSIS NOTES (11.4)

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  1. MEIOSIS NOTES (11.4)

  2. Reproduction • Asexual (relies on mitosis): all of the parents DNA goes to the offspring • Sexual (relies on meiosis): used to create sex cells

  3. 2 TYPES OF CELLS • BODY CELLS • SEX CELLS

  4. Types of Cells: Body Cells All cells other than sex cells -Also called somatic cells -Made by mitosis This scanning electron micrograph (courtesy of Dr. Marion J. Barnhart) shows the characteristic biconcave shape of red blood cells.

  5. Types of Cells: Body Cells -Contain 2 copies of each chromosome -called homologous chromosomes -have diploid #, 2n EX. Humans =46

  6. Types of Cells: Sex Cells *Also called gametes *Eggs and sperm *Made by meiosis *Have haploid #, n *EX. Humans =23

  7. Sex Cells (sea urchin egg being fertilized)

  8. Chromosome # Egg (haploid #) Sperm(haploid #) ZYGOTE (diploid #) Ex. Humans 23 + 23 =46

  9. Meiosis: produces sex cells Reduction division -starts with 1 diploid cell and ends up with 4 haploid cells

  10. Meiosis occurs in 2 steps MEIOSIS I AND MEIOSIS II

  11. MEIOSIS I Meiosis I (P1, M1, A1, T1) -homologous chromosome pairs are divided -two new daughter cells are produced -reduction division

  12. MEIOSIS II Meiosis II (P2, M2, A2, T2) • Two sister chromatids are split into two daughter cells • Analagous to mitosis because chromosome # stays the same

  13. Meiosis Diagram

  14. CROSSING OVER Occurs during Prophase I of meiosis Tetrads form and DNA is exchanged XXXX ADVANTAGE: genetic variation

  15. Adapted from: Morgan T.H., Sturtevant A.H., Muller H.J., and Bridges C.B., "The Mechansim of Mendelian Heredity", 1915. Crossing Over

  16. MALES Meiosis occurs in testes at puberty and then occurs as needed 1 spermatocyte=4 sperm FEMALES Meiosis occurs in the ovaries before birth 1 oocyte=1 egg and 3 wasted cells Gamete Development in Males and Females

  17. Sperm Formation

  18. Egg Formation (unequal cytokinesis)

  19. Comparing Mitosis and Meiosis HOW MANY CELLS ARE MADE? Mitosis 2 Meiosis 4

  20. Comparing Mitosis and Meiosis ARE RESULTING CELLS GENETICALLY THE SAME OR DIFFERENT? Mitosis Genetically the same Meiosis Genetically different

  21. Comparing Mitosis and Meiosis WHAT TYPES OF CELLS RESULT IN THE PROCESS? (BODY CELLS OR GAMETES) Mitosis Body cells Meiosis Gametes

  22. Comparing Mitosis and Meiosis WHAT ARE THE ADVANTAGES OF EACH PROCESS? Mitosis Growth and repair Meiosis Formation of sex cells and genetic variation