Chapter 10 Cell Growth and Division

1. Chapter 10 Cell Growth and Division

2. I. Cell Growth A. When cells are NOT dividing, DNA is found in the nucleus in the form of uncoiledchromatin. 1. What does this look like in the cell? A mass of genetic material that is spread out; a bowl of spaghetti.

3. I. Cell Growth 2. When the cell is getting ready to divide, chromosomes form as the DNA wraps around histones.

4. I. Cell Growth B. Chromosomes – carriers of genetic information that is copied and passed to new cells 1. Gene – section of DNA that controls production of a protein; found on a chromosome

5. I. Cell Growth 2. Structure of Chromosomes a. Each chromosome consists of two identical halves. These halves are known as sister chromatids. b. Joining the pair of chromatids together is a centromere. This holds them together until they separate at cell division.

6. I. Cell Growth c. What does this look like in the cell?

7. I. Cell Growth 3. Chromosome Numbers a. Each organism has a characteristic number of chromosomes. - Fruit flies = 8 chromosomes (4 pair) - Adder’s Tongue Fern = 1, 262 chromosomes (631 pairs) - Humans = 46 chromosomes (23 pairs)

8. I. Cell Growth

9. I. Cell Growth C. Two types of Chromosomes 1. Sex Chromosomes – determine the sex of an organism; humans have 2 of these chromosomes (1 pair) a. Male = XY, Female = XX

10. I. Cell Growth 2. Autosomes – the remaining body chromosomes; humans have 44 of these. They will “travel in pairs”, as homologous chromosomes.

11. I. Cell Growth 3. This means you have 2 of every chromosome, they carry genes for the same traits, but they are NOT identical. a. Where do they come from? You receive 1 chromosome from each parent! b. Example: Chromosome 19 contains genes for hair color. Mom’s #19 could have the “blonde” hair gene and Dad’s #19 could the “brown” hair gene.

12. I. Cell Growth D. Chromosomes in Each Cell 1. Diploid – a cell containing 2 copies of each chromosome (both chromosomes in the homologous pair) a. Abbreviated: 2N b. Human example: skin cells, muscle cells (any BODY cell), 2N = 46

13. I. Cell Growth 2. Haploid – a cell containing 1 copy of each chromosome a. Abbreviated: N b. Human example: sperm and eggs cells (any SEX/gamete cell), N =23

14. I. Cell Growth E. Cell Size Limits 1. Organisms grow by producing more cells. a. Cell size is usually comparable between a young and old animal; the older animal just has more of them.

15. I. Cell Growth 2. Why can’t cells continually grow larger? a. DNA “Overload” – it can no longer meet all the cells needs/demands

16. I. Cell Growth b. Exchanging materials - Rate at which materials are exchanged depends on the cellmembrane(surface area of the cell). - Rate at which materials are used (oxygen, water) or produced (waste) depends on the volume of the cell.

17. I. Cell Growth c. As the length of the cell increases, the volumeincreases faster than the surface area. d. It is hard for the cells to keep up with moving materials and wastes in and out, so the cell divides.

18. II. Cell Division A. Cell division performed by prokaryotes is a simple process. Two identical cells are created from one cell through the process of binary fission. 1. Steps of Binary Fission a. Chromosome attached to inside of cell membrane makes a copy of itself.

19. II. Cell Division b. Cell begins to growuntil it is about two times the size of parent cell. c. A new cell wall forms between the two chromosomes; cell splits into twonew cells.

20. II. Cell Division B. Two Types of Cell Division in Eukaryotes 1. Mitosis – cell division that produces bodycells identical to the original parent cell (diploid) a. Examples of cells that do this: skin, muscle, heart 2. Meiosis – cell division that produces gametes(sex cells) with half the number of chromosomes as the parent cell (haploid) a. Examples of cells that do this: sperm and egg; GAMETES ONLY

21. II. Cell Division C. Cell Cycle – sequences of growth and division of the cell 1. Three Steps of the Cell Cycle a. Interphase (most time spent here) b. Mitosis c. Cytokinesis

22. II. Cell Division How long does it take for a cell to go through one cell cycle? It all depends on the cell. A human liver cell, for example, completes one cell cycle in about 22 hours, as shown in the graph.

23. II. Cell Division D. Cell Cycle in Detail 1. Interphase - time when the cell is NOTdividing a. Three Phases of Interphase - G1 - cell grows, makes organelles - S - DNA copied (synthesized) - G2 - cell makes centrioles; normal metabolism; preparing to divide

24. II. Cell Division 2. Mitosis- dividing of the cell’s nucleus • FOUR PHASES OF MITOSIS • a. Prophase • b. Metaphase • c. Anaphase • d. Telophase

25. II. Cell Division a. Four Phase of Mitosis - Prophase- longest phase of mitosis • Chromatin coils into visible chromosomes (sister chromatids) • Nuclear envelope/membrane starts to disappear • Spindle fibers appear from centrioles (animal cells only)

26. II. Cell Division - Metaphase- shortest phase of mitosis • Spindles attach and move chromosomes to line up along the equator (middle) of the cell

27. II. Cell Division - Anaphase - • Chromosomes are pulled apart at the centromere by spindles and separated into sister chromatids

28. II. Cell Division - Telophase- • Sister chromatids reach opposite poles (sides of the cell) • Spindles disappear • Nuclear envelopes/membranes reappear • Cell begins to split into 2 new cells

29. II. Cell Division - Cytokinesis- dividing of the cell’s cytoplasm, forming two new cells • Animal cells: 2 new cells are separated by the cytoplasm “pinching in”

30. II. Cell Division • Plant cells: 2 new cells separated by a cell plate that helps form the cell walls

31. II. Cell Division - Cytokinesis-

32. II. Cell Division E. Meiosis 1. Meiosis - Cell division that produces gametes with half the number of chromosomes as the parent cell (haploid) a. 2 separate cell divisions: meiosis I and meiosis II - Interphase and cytokinesis occur with both divisions

33. II. Cell Division b. Meiosis starts with 1 diploid cell and ends with 4 haploid cells; Each gamete has half the number of chromosomes as a diploid cell. 1 diploid cell with 4 chromosomes 4 haploid cells with 2 chromosomes each

34. II. Cell Division F. Steps of Meiosis 1. MEIOSIS I a. Prophase I - • DNA coils into tetrads (pair of homologous chromosomes) • Spindles appear • Nuclear envelope/membrane disappears • Crossing over occurs - DNA is swapped between chromosomes in a pair

35. II. Cell Division b. Metaphase I­- • Tetrads are moved by the spindles and line up along the middle/equator of the cell.

36. II. Cell Division c. Anaphase I - • Tetrads pulled apart by the spindles and separated into chromosomes • Chromosomes begin moving to opposite ends of the cell

37. II. Cell Division d.Telophase I - • Chromosomes reach opposite sides of the cell • Spindle disappears • Nuclear envelope/membrane reappears • Cytokinesis occurs after this step, forming two new cells, which then go through interphase again

38. II. Cell Division • Meiosis II--has 4 stages, PMAT II • Each stage--occurs just like the stages of mitosis Prophase II Metaphase II Anaphase II Telophase II

39. II. Cell Division 2. MEIOSIS II a. Prophase II - • Spindle appear in each of the 2 new cells • Nuclear envelopes/membranes disappears

40. II. Cell Division b. Metaphase II - • Sister chromatids line up in the middle/equator of the cell.

41. II. Cell Division c. Anaphase II - • Spindles split centromeres and sister chromatids separate • Chromatids start to move to opposite ends of the cell

42. II. Cell Division d. Telophase II - • Sister chromatids (haploid) reach opposite ends of the cell • Spindles disappear • Nuclear envelopes/membranes appear • Cytokinesis follows this step forming four new cells

43. II. Cell Division G. Soooooooooooo, what happens after meiosis? 1. Sexual Reproduction - production and combination of gametes a. Fertilization- fusion of male and female gametes to form zygote • Zygote - diploid cell (2 of each chromosome) http://video.sciencemag.org/VideoLab/2127025888001/1/medicine

44. Comparison of Types of Division