Cell Division


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Cell Division

  1. 1. Cell Division
  2. 2. DNA <ul><li>DNA – large molecule that stores hereditary (genetic) information. </li></ul><ul><li>- found in the nucleus of a cell . </li></ul><ul><li>- controls cell division . </li></ul><ul><li> </li></ul>
  3. 3. Chromosomes <ul><li>Chromosomes – MANY strands of DNA wound together into threadlike structures. </li></ul>
  4. 4. Cell Division <ul><li>Cell Division – a cell that is dividing into two new cells. </li></ul><ul><li>- the two new cells are daughter cells . </li></ul>
  5. 5. Mitosis <ul><li>Mitosis – two daughter cells with exact same genetic material (DNA) are produced. </li></ul><ul><li>- daughter cells have same number of chromosomes as parent cell . </li></ul>6 chromosomes 6 chromosomes 6 chromosomes
  6. 6. Interphase <ul><li>Interphase – preparation stage BEFORE Mitosis where the cell grows and duplicates materials. </li></ul><ul><li>- Longest stage of Cell Cycle </li></ul><ul><li>- Copies chromosomes ! </li></ul><ul><li>- Organelles double. </li></ul>                            
  7. 7. Prophase <ul><li>Prophase – first phase of Mitosis where DNA winds into chromosomes . </li></ul>
  8. 8. Prophase Chromosomes
  9. 9. Metaphase <ul><li>Metaphase – chromosomes line up along the middle of the cell. </li></ul>
  10. 10. Metaphase Chromosomes Middle (equator) of cell
  11. 11. Anaphase <ul><li>Anaphase – chromosomes are “ pulled ” apart! </li></ul><ul><li> - move to opposite sides of cell. </li></ul>
  12. 12. Anaphase Single Chromosome
  13. 13. Telophase <ul><li>Telophase – “ ending ” phase of Mitosis. </li></ul><ul><li>- two new cells form. </li></ul>
  14. 14. Telophase New nuclei Chromosomes unwinding
  15. 15. End Results of Mitosis 4 chromosomes at start Chromosomes double into 2 strands (8) 4 chromosomes in each new cell at end
  16. 16. What kinds of cells do Mitosis? <ul><li>Single-celled organisms - mitosis as a form of asexual reproduction. </li></ul><ul><li>Multicellular organisms - mitosis in repair and replacement of body cells (hair, skin, etc.) </li></ul>
  17. 17. Cancer: Uncontrolled Division <ul><li>Normal cells will stop dividing when they come in contact with other cells . </li></ul><ul><li>Cancer – disease where cells do not stop dividing and ignore signals from other cells. </li></ul>
  18. 18. What is the Purpose of Reproduction? <ul><li>To form new individuals ( offspring ) of a species . </li></ul><ul><li>2 Types: </li></ul><ul><li>Asexual Reproduction – reproduction involving only one parent. </li></ul><ul><li>Sexual Reproduction – reproduction involving two parents. </li></ul>
  19. 19. Asexual Reproduction <ul><li>Offspring are identical and contain same amount of genetic material as parents . </li></ul><ul><li>- Results from mitosis . </li></ul><ul><li>Ex: a. Budding </li></ul><ul><li> b. Binary Fission </li></ul><ul><li>c. Vegetative Propogation </li></ul><ul><li> d. Sporulation </li></ul><ul><li> e. Regeneration </li></ul>
  20. 20. Sexual Cell Division: Meiosis
  21. 21. Chromosome Number <ul><li>Human body cell – 46 chromosomes </li></ul><ul><li>Arranged in 23 pairs (23 X 2=46). </li></ul><ul><li>Homologous Chromosomes – a pair of chromosomes with same size, shape, etc. </li></ul>
  22. 22. Diploid <ul><li>Diploid – body cells that contain two sets of chromosomes. </li></ul><ul><li>- Ex: skin, hair, heart, liver, muscle cells, etc. </li></ul><ul><li> - Written as 2n . </li></ul>
  23. 23. Haploid <ul><li>Haploid – gamete (sex) cells which contain only one set of chromosomes. </li></ul><ul><li>- Ex: sperm/egg cells. </li></ul><ul><li>- Written as n . </li></ul>
  24. 24. Meiosis <ul><li>Meiosis – type of cell division used to produce gametes (sex cells). </li></ul><ul><li>Two functions: </li></ul><ul><li>Forms cells with half the number of chromosomes. (23 chromosomes in both egg and sperm) </li></ul><ul><li>Rearrange chromosomes for genetic differences from parents ( variability ). </li></ul><ul><li>Two sets of phases whereas Mitosis only has one set. </li></ul>
  25. 25. Meiosis Overview 4 Chromosomes 2 Chromosomes in each cell
  26. 26. Meiosis in Males <ul><li>Meiosis in males produces four sperm (n) cells which are all functional. </li></ul>2n n n n n
  27. 27. Meiosis in Females <ul><li>Meiosis in females produces four egg (n) cells . Only one is functional! </li></ul>2n n n n n
  28. 28. Meiosis = Genetic Variation <ul><li>Meiosis is responsible for genetic differences in new cells: </li></ul><ul><li>Chromosomes lineup in different ways. </li></ul><ul><li>Crossing over – swapping pieces of chromosomes. </li></ul>
  29. 29. Mitosis Vs. Meiosis <ul><li> Mitosis Meiosis </li></ul><ul><li># of parent cells 1 2 </li></ul><ul><li># of cells produced 2 4 </li></ul><ul><li>Appearance of Identical Different </li></ul><ul><li>offspring </li></ul><ul><li>Types of cells Body Gametes </li></ul><ul><li> (egg/sperm) </li></ul>
  30. 31. Meiosis I <ul><li>Interphase I – DNA is unwound as chromatin. </li></ul><ul><li>- DNA duplicates. </li></ul>
  31. 32. <ul><li>Prophase I –chromosomes become visible and double-stranded. </li></ul><ul><li>- Homologous chromosomes pair up. </li></ul><ul><li>- Crossing over – pieces of chromosomes are swapped. </li></ul>Homologous chromosomes Homologous chromosomes Meiosis I
  32. 33. <ul><li>Metaphase I – pairs of homologous chromosomes lineup in the middle of the cell. </li></ul>
  33. 34. <ul><li>Anaphase I – homologous chromosomes separate ( not into single-stranded chromosomes or chromatids ). </li></ul>
  34. 35. <ul><li>Telophase I – two haploid daughter cells are formed. </li></ul><ul><li>- nuclear membrane </li></ul><ul><li>returns! </li></ul>
  35. 36. Meiosis II (like Mitosis) <ul><li>Prophase II – two haploid daughter cells now enter meiosis II. </li></ul><ul><li>- cell has completely divided and chromosomes are separated. </li></ul>
  36. 37. <ul><li>Metaphase II – chromosomes (non-homologous) line up in the middle of each cell. </li></ul>
  37. 38. <ul><li>Anaphase II – double-stranded chromosomes split into single-stranded chromosomes ( chromatids ). </li></ul>
  38. 39. <ul><li>Telophase II – four haploid cells are formed each with single-stranded chromosomes ( chromatids ). </li></ul>