1. I. The Cell Cycle

2. Cell Cycle: the series of events that take place in a cell leading to its division and duplication *some cells, such as muscle and nerve cells, never divide

3. A. Parts of the Cell Cycle

4. 1. Interphase: The longest-lasting phase of the cell cycle in which a cell performs the majority of it’s function, such as preparing for nuclear division and cytokinesis

5. a. First Growth Phase (G 1 ): i. cell grows rapidly ii. organelles are duplicated iii. cells that are not dividing remain in this phase

6. b. Synthesis (S): i.DNA is copied -Genetic material in the cell doubles -This forms loosely coiled chromosomes

7. c. Second Growth Phase (G 2 ): i. Preparations are made for the nucleus to divide ii. Microtubules are assembled into centrioles to move the chromosomes

9. 2. Mitosis: a nuclear division resulting in the production of two somatic cells having the same genetic complement as the original cell a. Forms diploid cells i. Diploid: a cell that contains 2 sets of chromosomes (ex: human diploid # is 46) b. Forms somatic cells i. Somatic cells: body cells

10. c. The Steps of Mitosis

11. 1. Prophase i. Chromosomes become visible ii. Nuclear membrane and nucleolus break down iii. Centrioles begin to move to opposite sides of the cell

14. 2. Metaphase (middle) i.Centrioles produce spindles ii.Paired chromatids move to the equator (middle) of the cell iii.Spindle fibers attach to the centromeres on the sister chromatids

17. 3. Anaphase (apart) i. Spindles shorten, pulling the sister chromatids apart. ii. An equal number of chromosomes move to each pole of the cell

20. 4. Telophase i. Spindle fibers disappear ii. Nucleolus reappears iii. Nuclear membrane forms around the 2 sets of chromosomes iv. Chromosomes unwind

23. 3. Cytokinesis a. This may begin during teolophase b. Cytoplasm is divided in half c. 2 separate cells are formed d. Each cell receives an identical copy of the original chromosomes and half of its cytoplasm

24. e. In animal cells, the cell is pinched in half by a belt of protein threads f. In plant cells, vesicles fuse at the midline and form a cell plate

25. END RESULT a. 2 new cells with the same genetic info as the original cell b. Process used for the growth and repair of body cells

26. II. Changes in Mitosis

27. A. Cancer: The uncontrolled growth of cells

28. 1. Causes of Cancer a. Mutations i. Mutations that cause over-producing growth promoting molecules which speeds up the cell cycle ii. Mutations that Inactivate proteins that slow or stop the cycle

29. Continued… b. Environment i. Tobacco ii. UV radiation iii. Viruses iv. Chemicals

30. 2. Types of Cancer a.Benign: cancer cells that remain at the original site b.Malignant: cancer spreads to neighboring tissues and other parts of the body

31. c. Examples i. Melanoma: skin cancer ii. Leukemia: blood cancer iii. Lymphoma: immune system cancer

32. III. Asexual Reproduction A single parent passes copies of all of its genes to each of its offspring A. Binary Fission: a form of asexual reproduction that produces identical offspring 1. Used by bacteria

33. B. Budding New individuals split off from existing ones 1. Used by yeast, hydra, and sponges

34. IV. Sexual Reproduction Two parents form haploid reproductive cells, which join to form offspring

35. A. Meiosis: a two-phase nuclear division that results in the eventual production of gametes with half the normal number of chromosomes

36. 1. Gamete: a specialized cell (egg or sperm) used in sexual reproduction 2. Forms haploid cells a. Haploid: a cell that contains only 1 set of chromosomes (human egg or sperm haploid # is 23) 3. Meiosis involves 2 divisions of the nucleus

37. 4. Steps of Meiosis a. Prophase I -chromosomes condense -nuclear envelope breaks down -homologous chromosomes pair *Homologous chromosomes: chromosomes that are similar in size, shape, and genetic content.

38. Prophase I cont… -Crossing-over: an exchange of genetic material between homologous chromosomes; contributes to the genetic variability in offspring

40. b. Metaphase I -pairs of homologous chromosomes move to the equator -Spindles attach to the centromeres of the sister chromatids

42. c. Anaphase I -Spindles shorten -homologous chromosomes separate, chromatids stay together

44. d. Telophase I -individual chromosomes gather at each pole -cytoplasm divides, forming 2 new cells

45. e. Prophase II -a new spindle forms around the chromosomes

47. f. Metaphase II -chromosomes line up at the equator and spindle fibers attach to their centromeres

49. g. Anaphase II -spindles shorten -centromeres divide -chromatids are pulled to opposite poles

51. h. Telophase II -nuclear envelope forms around each set of chromosomes -cytokinesis occurs END RESULT: 4 haploid cells

53. 5. Meiosis in Males a. Spermatogenesis: process by which sperm are produced in male animals

54. 6. Meiosis in Females a. Oogenesis: process by which eggs are produced in female animals

56. Mitosis versus Meiosis

57. -1 cell division -results in 2 cells -chromosomes # stays the same -results in growth and repair Mitosis -used in body cells -chromosomes line up at the center of the cell -centromeres divide -centrioles are in pairs -PMAT Meiosis -2 cell divisions -results in 4 cells -chromosome # is divided in half -produces gametes (egg and sperm) -crossing-over occurs -Forms diploid cells -Forms haploid cells