1. Cells! Most cells are between 2µm and 200µm
A micrometer is 1 millionth of a meter!
Too small to be seen with naked eye

2. Your body cells are the same size as when you were born!

3. Why can’t organisms be one big giant cell?

4. Limits Diffusion limits cell size
A cell 20 cm wide would require months for nutrients to get to the center

5. Limits Metabolism limits cell size Larger cells produce more waste
Larger cells require more materials

6. Surface Area : Volume
All cells want:
Surface Area Volume

7. Limits DNA limits cell size Larger cells need more DNA
(more things to manage)

8. So, if too big is a problem, what’s the solution?
Cellular Division!

9. Cellular Division
Process by which a growing cell divides forming two “daughter” cells

10. Keeping Cells Identical
The instructions for making cell parts are encoded in the DNA
Each new cell must get a complete set of the DNA molecules

11. Two new, identical DNA strands
DNA Replication
Original DNA strand
DNA must be copied or replicated before cell division
Each new cell will then have an identical copy of the DNA
Two new, identical DNA strands

12. Identical Daughter Cells
Two identical daughter cells
Parent Cell

13. Asexual Reproduction
A single cell dividing to make 2 new, identical daughter cells
Binary Fission
Mitosis
Occur in somatic cells (body cells)
Diploid number of chromosomes (2n)

14. Prokaryotic Chromosome
The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane

15. Steps in Binary Fission
Cells increase their cell mass slightly
DNA & cell components are replicated
Each cell divides into 2 daughter cells 15

16. E. Coli Dividing by Binary Fission16

17. Eukaryotic Chromosomes
All eukaryotic cells store genetic information in chromosomes
Most eukaryotes have between 10 and 50

18. Eukaryotic Chromosomes
Human body cells have 46 chromosomes or 23 identical pairs

19. Eukaryotic Chromosomes
Each chromosome is composed of a single, tightly coiled DNA molecule
Chromatin

20. Compacting DNA into Chromosomes
DNA is tightly coiled around proteins called histones

21. Chromosomes in Dividing Cells
Duplicated chromosomes are called chromatids
Held together by the centromere
Called Sister Chromatids

22. DNA Vocabulary DNA in nucleus is a mass of chromatin
Chromatin condenses into chromosomes
…which duplicate to form sister chromatids
Sister chromatids can be called a chromosome as well!

23. Karyotype
A picture of the chromosomes from a human cell arranged in pairs by size

24. Karyotype First 22 pairs are called autosomes
Last pair are the sex chromosomes
XX female or XY male

25. The Y Chromosome Decides
Boy or Girl?
The Y Chromosome Decides
Y - Chromosome
X - Chromosome

26. Steps in Binary Fission
Review! 26

27. E. Coli Dividing by Binary Fission27

28. Chromosomes in Dividing Cells

29. Cell Life Cycle What does the cell do in its life time? Growth (G1)
Synthesis (S)
Growth (G2)
Mitosis
Cytokinesis

30. Mitosis The Different Steps

31. What does a cell need TO DO to divide?
Interphase
Grow- gets bigger
Synthesize- copy DNA
Grow again- double its organelles
Time frame varies
Different cells divide at different rates

32. Mitosis Division of the nucleus Only occurs in eukaryotes
Doesn’t occur in some cells such as brain cells

33. Mitosis 1. Prophase Nuclear envelope disappears
Chromatin condenses into chromosomes
Spindle fibers begin to attach centrioles to the chromosomes at the centromere

34. Mitosis
2) Metaphase
Chromosomes line up in the center

35. Mitosis 3) Anaphase Sister chromatids separate
Spindles pull them apart towards the opposite ends of the cell

36. Mitosis
4) Telophase
Sister chromatids are at ends
Cytokinesis begins

37. Cytokinesis Means division of the cytoplasm
Division of cell into two, identical halves called daughter cells
Begins interphase again

38. Cytokinesis In animal cells, cleavage furrow forms to split cell
In plant cells, cell plate forms at the equator to divide cell

39. Cleavage furrow in animal cell Cell plate in plant cell
Cytokinesis
Cleavage furrow in animal cell
Cell plate in plant cell

40. Daughter Cells of Mitosis
Have the same number of chromosomes as each other and as the parent cell from which they were formed
Identical to each other, but smaller than parent cell
Must grow in size to become mature cells (G1 of Interphase)

41. Identical Daughter Cells
What is the 2n or diploid number? 2
Chromosome number the same, but cells smaller than parent cell

42. Watch the clip!

43. Mitosis Video Clip

44. Regulating the Cell Cycle
CYCLINS - proteins that regulate the cell cycle in eukaryotes
Internal regulators – respond to events inside the cell
Example: don’t start metaphase until chromosomes are in pairs
External regulars – respond to events outside the cell
Example: sense cells nearby

45. Regulating the Cell Cycle
CANCER = disease of mitosis
Cells not responding to signals to stop dividing!
Missing density-dependent signals

46. cell cycle Healthy, dividing cell Damage to cell Damage control
Stop cell division
Assess damage
Cellular repair
Successful repair
Return to
cell cycle
Failed repair
Cancer
Extensive damage
Cell death
modified from Biology of Cancer by R.W. Phillis and S. Goodwin

47. Four Mitotic Stages
Prophase
Metaphase
Anaphase
Telophase

48. Review of Mitosis

49. Mitosis in Onion Root Tips
Do you see any stages of mitosis?

50. Name the Stages of Mitosis:
Early Telophase,
Early prophase
Early Anaphase
Interphase
Metaphase
Late Prophase
Cytokinesis
Mid-Prophase
Late Anaphase

51. Early, Middle, & Late Prophase Telophase & Cytokinesis
Identify the Stages ?
Early, Middle, & Late Prophase ? ? ?
Metaphase
Anaphase
Late Prophase ? ? ?
Telophase & Cytokinesis
Late Anaphase
Telophase

52. Locate the Four Mitotic Stages in Plants
Anaphase
Telophase
Metaphase
Prophase

53. Types of Reproduction
Asexual Reproduction: a single cell dividing to make 2 new, identical daughter cells
Examples:
Binary Fission
Mitosis

54. Types of Reproduction
Asexual Reproduction: a single cell dividing to make 2 new, identical daughter cells
Occur in somatic cells (body cells)
Diploid number of chromosomes (2n)

55. Types of Reproduction
Sexual Reproduction: a single cell dividing to make 4 new, genetically different daughter cells
Occur in gametes (sex cells)
Haploid number of chromosomes (1n)
Daughter cells are NOT identical

56. Types of Reproduction
Sexual Reproduction: a single cell dividing to make 4 new, genetically different daughter cells
Example:
Meiosis (more on this later…)

57. Microscope Review What is the correct way to hold a microscope?
Two hands!
Support arm and base of microscope!
What objective lens do I use to first focus an image?
low

58. Microscope Review
When do you use the coarse adjustment knob?
ONLY ON LOW
NEVER TOUCH COARSE ADJUSTMENT ON ANY OTHER OBJECTIVES!
If I am looking at an image on the 40x objective lens, what is my TOTAL magnification?
40x objective x 10x ocular = 400x total magnification

59. Your Turn!
Mitosis Microscope Lab