1. MITOSIS AND MEIOSIS

2. Cell Replication Eukaryotic cell replication Eukaryotic cell replication Cells duplicate Cells duplicate Divide into two daughter cells. Divide into two daughter cells.

3. Mitosis exact copy of the original cell exact copy of the original cell Includes an exact replication of DNA Includes an exact replication of DNA Millions of rounds of mitosis take place during the development of large multicellular organisms Millions of rounds of mitosis take place during the development of large multicellular organisms

4. Meiosis The creation of sex cells The creation of sex cells Sperm and Egg Cells Sperm and Egg Cells

5. The Cell Cycle The cell cycle is the recurring sequence of events that includes the duplication of a cell’s contents and its subsequent division. The cell cycle is the recurring sequence of events that includes the duplication of a cell’s contents and its subsequent division. The cell cycle is divided into three phases: The cell cycle is divided into three phases: Interphase Interphase Mitosis Mitosis Cytokinesis Cytokinesis

7. Interphase 3 parts: G1, S, G2 Cell copies its DNA Prepares for mitosis growing to a size that can support cell division, replicating its DNA.

8. DNA Replication (S phase) Summary DNA (double helix) replicates so that from one helix of DNA emerge two “daughter” helices. DNA (double helix) replicates so that from one helix of DNA emerge two “daughter” helices. Daughter helices are exact copies of the parental helix. Daughter helices are exact copies of the parental helix. DNA creates daughter helices by using the parental strands of DNA as a template. DNA creates daughter helices by using the parental strands of DNA as a template.

9. DNA Replication

10. Products of Replication Interphase: every chromosome is replicated Interphase: every chromosome is replicated In a human cell, all 46 chromosomes are replicated, doesn’t double In a human cell, all 46 chromosomes are replicated, doesn’t double Instead, each of the two new chromosomes are joined together at their middle by a region called a centromere. Instead, each of the two new chromosomes are joined together at their middle by a region called a centromere. The result is an X-shaped structure The result is an X-shaped structure

11. New Chromosome

12. Mitosis Three things must happen: DNA packaged into chromosomes must replicate. DNA packaged into chromosomes must replicate. Copies of the chromosomes and organelles must migrate to opposite ends of the cell. Copies of the chromosomes and organelles must migrate to opposite ends of the cell. The cell must physically split into two separate cells. The cell must physically split into two separate cells.

13. Mitosis Prophase Prophase Metaphase Metaphase Anaphase Anaphase Telophase TelophasePMAT!!!

14. Microscopic Prophase

16. Metaphase

18. Metaphase

19. Anaphase

21. Anaphase

22. Telophase

24. Telophase

25. Cytokinesis Although mitosis officially ends with telophase, at this point, the cell is not yet actually split into two new cells. Although mitosis officially ends with telophase, at this point, the cell is not yet actually split into two new cells. The final cleavage is not exactly its own stage, but it does have its own name: cytokinesis, literally “cell division.” The final cleavage is not exactly its own stage, but it does have its own name: cytokinesis, literally “cell division.”

28. Cell Cycle Animation http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chap ter2/animation__how_the_cell_cycle_works.ht ml http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chap ter2/animation__how_the_cell_cycle_works.ht ml

29. Basis of Inheritance: Meiosis Mitosis takes a diploid cell and creates a nearly exact copy. Mitosis takes a diploid cell and creates a nearly exact copy. Mitosis has two main functions: Mitosis has two main functions: (1) the creation of all of the somatic (body) cells in humans and other living organisms (1) the creation of all of the somatic (body) cells in humans and other living organisms (2) in organisms that undergo asexual reproduction (2) in organisms that undergo asexual reproduction

30. Why is meiosis necessary? This diversity of chromosomes is the result of sexual reproduction, which involves the contribution of the genetic material from not one, but two parents. This diversity of chromosomes is the result of sexual reproduction, which involves the contribution of the genetic material from not one, but two parents. During sexual reproduction the father’s haploid sperm cell and the mother’s haploid ovum (egg) cell fuse to form a single-celled diploid zygote that then divides billions of times to form a whole individual. During sexual reproduction the father’s haploid sperm cell and the mother’s haploid ovum (egg) cell fuse to form a single-celled diploid zygote that then divides billions of times to form a whole individual.

31. What is meiosis? In order for sexual reproduction to take place, however, the parents first need to have haploid sperm or ova, also called sex cells, germ cells, or gametes. In order for sexual reproduction to take place, however, the parents first need to have haploid sperm or ova, also called sex cells, germ cells, or gametes. Meiosis is the name for the special type of cell division that produces gametes. Meiosis is the name for the special type of cell division that produces gametes.

32. Process of Meiosis Meiosis involves two cellular divisions: meiosis I and meiosis II. Meiosis involves two cellular divisions: meiosis I and meiosis II. Each stage of meiosis runs through the same five stages as discussed in mitosis. Each stage of meiosis runs through the same five stages as discussed in mitosis. During the first round of division, two intermediate daughter cells are produced. During the first round of division, two intermediate daughter cells are produced. By the end of the second round of meiotic division (meiosis II), the original diploid (2n) cell has become four haploid (n) daughter cells. By the end of the second round of meiotic division (meiosis II), the original diploid (2n) cell has become four haploid (n) daughter cells.

34. Meiosis I Interphase I Interphase I DNA replication DNA replication After replication, the cell has a total of 46 chromosomes, each made up of two sister chromatids joined by a centromere. After replication, the cell has a total of 46 chromosomes, each made up of two sister chromatids joined by a centromere.

35. Meiosis I PROPHASE I PROPHASE I The major distinction between mitosis and meiosis occurs during this phase. The major distinction between mitosis and meiosis occurs during this phase.

36. Meiosis I : Prophase I In mitotic prophase, the double-stranded chromosomes line up individually along the spindle. In mitotic prophase, the double-stranded chromosomes line up individually along the spindle. But in meiotic prophase I, chromosomes line up along the spindle in homologous pairs. But in meiotic prophase I, chromosomes line up along the spindle in homologous pairs. Then, in a process called synapsis, the homologous pairs actually join together and intertwine, forming a tetrad (two chromosomes of two chromatids each, or four total chromatids). Then, in a process called synapsis, the homologous pairs actually join together and intertwine, forming a tetrad (two chromosomes of two chromatids each, or four total chromatids).

37. Meiosis I : Prophase I Often this intertwining leads the chromatids of homologous chromosomes to actually exchange corresponding pieces of DNA, a process called crossing-over or genetic reassortment. Often this intertwining leads the chromatids of homologous chromosomes to actually exchange corresponding pieces of DNA, a process called crossing-over or genetic reassortment. Throughout prophase I, sister chromatids behave as a unit and are identical except for the region where crossover occurred. Throughout prophase I, sister chromatids behave as a unit and are identical except for the region where crossover occurred.

38. Meiosis I : Metaphase I The nuclear membrane breaks down, allowing microtubules access to the chromosomes. The nuclear membrane breaks down, allowing microtubules access to the chromosomes. Still joined at their crossover regions in tetrads, the homologous pairs of chromosomes, with one maternal and one paternal chromosome in each pair Still joined at their crossover regions in tetrads, the homologous pairs of chromosomes, with one maternal and one paternal chromosome in each pair The pairs align in random order. The pairs align in random order.

39. Meiosis I : Anaphase I In contrast to mitosis, the centromeres do not split In contrast to mitosis, the centromeres do not split the entire maternal chromosome of a homologous pair is pulled to one end the entire maternal chromosome of a homologous pair is pulled to one end the paternal chromosome is pulled to the other end the paternal chromosome is pulled to the other end

40. Meiosis I : Telophase The chromosomes arrive at separate poles and decondense The chromosomes arrive at separate poles and decondense Nuclear membranes re-form around them Nuclear membranes re-form around them The cell physically divides, as in mitotic cytokinesis. The cell physically divides, as in mitotic cytokinesis.

41. Product of Meiosis I Meiosis I results in two independent cells. Meiosis I results in two independent cells. One cell contains the maternal homologous pair, with a small segment of the paternal chromosome from crossover. One cell contains the maternal homologous pair, with a small segment of the paternal chromosome from crossover. The other cell contains the paternal homologous pair, likewise with a small segment of the maternal chromosome. The other cell contains the paternal homologous pair, likewise with a small segment of the maternal chromosome.

42. Product differences from Mitosis The cells produced in meiosis I are different from those produced in mitosis because both haploid members of the meiotic pair derive from random assortments of either the maternal or paternal chromosomes from each homologous pair (with the exception of the small crossover sections). The cells produced in meiosis I are different from those produced in mitosis because both haploid members of the meiotic pair derive from random assortments of either the maternal or paternal chromosomes from each homologous pair (with the exception of the small crossover sections).

43. Product differences in Meiosis In mitosis, the cellular division separates sister chromatids and results in diploid cells containing one maternal and one paternal copy in each diploid pair In mitosis, the cellular division separates sister chromatids and results in diploid cells containing one maternal and one paternal copy in each diploid pair

44. Meiosis II These cells do not undergo DNA replication before entering meiosis II. These cells do not undergo DNA replication before entering meiosis II. The two cells that move from meiosis I into meiosis II are haploid—each have 23 replicated chromosomes, rather than the 46 that exist in cells entering both mitosis and meiosis I. The two cells that move from meiosis I into meiosis II are haploid—each have 23 replicated chromosomes, rather than the 46 that exist in cells entering both mitosis and meiosis I.

45. Meiosis II To distinguish the phases, they are called prophase II, metaphase II, anaphase II, and telophase II. To distinguish the phases, they are called prophase II, metaphase II, anaphase II, and telophase II. One important difference between the events of meiosis I and II is that no further genetic reassortment takes place during prophase II. One important difference between the events of meiosis I and II is that no further genetic reassortment takes place during prophase II. As a result, prophase II is much shorter than prophase I. As a result, prophase II is much shorter than prophase I. In fact, all of the phases of meiosis II proceed rapidly. In fact, all of the phases of meiosis II proceed rapidly.

46. Meiosis II Metaphase II exactly the way it is in mitotic metaphase. Metaphase II exactly the way it is in mitotic metaphase. In anaphase II, the sister chromatids separate, once again in the same fashion as occurs in mitotic anaphase. In anaphase II, the sister chromatids separate, once again in the same fashion as occurs in mitotic anaphase. The only difference is that since there was no second round of DNA replication; only one set of chromosomes exists. When the two cells split at the end of meioisis II, the result is four haploid cells. The only difference is that since there was no second round of DNA replication; only one set of chromosomes exists. When the two cells split at the end of meioisis II, the result is four haploid cells.

47. Meiosis II Of the four haploid cells Of the four haploid cells One cell is composed completely of a maternal homologue, One cell is composed completely of a maternal homologue, One cell is a maternal homologue with a small segment of paternal DNA from crossover in meiosis I, One cell is a maternal homologue with a small segment of paternal DNA from crossover in meiosis I, Another is a complete paternal homologue Another is a complete paternal homologue The final paternal homologue with a small segment of maternal DNA from crossover in meiosis I The final paternal homologue with a small segment of maternal DNA from crossover in meiosis I

48. Meiosis II These four haploid cells are the gametes, the sperm or egg cells, that fuse together in sexual reproduction to create new individuals These four haploid cells are the gametes, the sperm or egg cells, that fuse together in sexual reproduction to create new individuals All four sperm cells will later mature All four sperm cells will later mature Only one egg cell will mature, the other 3 are polar bodies and die off Only one egg cell will mature, the other 3 are polar bodies and die off

49. Spermatogenesis and Oogenesis Meiosis can also be called gametogenesis, literally “creation of gametes.” Meiosis can also be called gametogenesis, literally “creation of gametes.” The specific type of meiosis that forms sperm is called spermatogenesis The specific type of meiosis that forms sperm is called spermatogenesis The formation of egg cells, or ova, is called oogenesis. The formation of egg cells, or ova, is called oogenesis.

50. Gametogenesis The most important thing you need to remember about both processes is that they occur through meiosis, but there are a few specific distinctions between them. The most important thing you need to remember about both processes is that they occur through meiosis, but there are a few specific distinctions between them.

51. Spermatogenesis The male testes have tiny tubules containing diploid cells called spermatogonium that mature to become sperm. The male testes have tiny tubules containing diploid cells called spermatogonium that mature to become sperm. The basic function of spermatogenesis is to turn each one of the diploid spermatogonium into four haploid sperm cells. The basic function of spermatogenesis is to turn each one of the diploid spermatogonium into four haploid sperm cells.

52. Spermatogenesis This quadrupling is accomplished through the meiotic cell division detailed in the last section. This quadrupling is accomplished through the meiotic cell division detailed in the last section. During interphase before meiosis I, the spermatogonium’s 46 single chromosomes are replicated to form 46 pairs of sister chromatids During interphase before meiosis I, the spermatogonium’s 46 single chromosomes are replicated to form 46 pairs of sister chromatids

53. Spermatogenesis In meiosis II, the two daughter cells go through a second division to yield four cells containing a unique set of 23 single chromosomes that ultimately mature into four sperm cells. In meiosis II, the two daughter cells go through a second division to yield four cells containing a unique set of 23 single chromosomes that ultimately mature into four sperm cells. Starting at puberty, a male will produce literally millions of sperm every single day for the rest of his life. Starting at puberty, a male will produce literally millions of sperm every single day for the rest of his life.

54. Spermatogenesis

55. Oogenesis Oogenesis involves the formation of haploid cells from an original diploid cell, called a primary oocyte, through meiosis. Oogenesis involves the formation of haploid cells from an original diploid cell, called a primary oocyte, through meiosis. The female ovaries contain the primary oocytes. The female ovaries contain the primary oocytes. There are two major differences between the male and female production of gametes. There are two major differences between the male and female production of gametes.

56. Oogenesis First of all, oogenesis only leads to the production of one final ovum, or egg cell, from each primary oocyte First of all, oogenesis only leads to the production of one final ovum, or egg cell, from each primary oocyte Of the four daughter cells that are produced when the primary oocyte divides meiotically, three come out much smaller than the fourth. Of the four daughter cells that are produced when the primary oocyte divides meiotically, three come out much smaller than the fourth.

57. Oogenesis These smaller cells, called polar bodies, eventually disintegrate, leaving only the larger ovum as the final product of oogenesis. These smaller cells, called polar bodies, eventually disintegrate, leaving only the larger ovum as the final product of oogenesis. The production of one egg cell via oogenesis normally occurs only once a month, from puberty to menopause. The production of one egg cell via oogenesis normally occurs only once a month, from puberty to menopause.

58. Oogenesis