1. Mitosis & Meiosis Chapters 9 & 10
Cell Division
Mitosis & Meiosis
Chapters 9 & 10

2. Cell Cycle

3. Ratio of Surface Area to Volume
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
Ratio of Surface Area to Volume

4. Chapter 9
Cellular Reproduction
9.1 Cellular Growth
As the cell grows, its volume increases much more rapidly than the surface area.
What’s the problem?
The cell might have difficulty supplying nutrients and expelling enough waste products.

5. Transport of Substances
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
Transport of Substances
Substances move by diffusion
Diffusion over large distances is slow and inefficient.
Small cells maintain more efficient transport systems.
Easier for things to pass through small cells.

6. Cellular Communications
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
Cellular Communications
The need for signaling proteins to move throughout the cell also limits cell size.
Cell size affects the ability of the cell to communicate instructions for cellular functions.

7. Cell division prevents the cell from becoming too large.
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
The Cell Cycle
Cell division prevents the cell from becoming too large.
It also is the way the cell reproduces so that you grow and heal certain injuries.
Cells reproduce by a cycle of growing and dividing called the cell cycle.

8. Chapter 9
Cellular Reproduction
9.1 Cellular Growth
Interphase is the stage during which the cell grows, carries out cellular functions, and replicates.
Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide.
Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell.

9. Chromosome Parts

10. The Stages of Interphase
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
The Stages of Interphase
The first stage of interphase, G1
The cell is growing, carrying out normal cell functions, and preparing to replicate DNA.

11. The Second Stage of Interphase, S
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
The Second Stage of Interphase, S
The cell copies its DNA in preparation for cell division.

12. The Third Stage of Interphase, G2
Chapter 9
Cellular Reproduction
9.1 Cellular Growth
The Third Stage of Interphase, G2
The cell prepares for the division of its nucleus.

13. Mitosis

14. Four Mitotic Stages
Prophase
Metaphase
Anaphase
Telophase

15. Spindle Fiber attached to Chromosome
Spindle fibers called kinetochores attach to the centromere of each chromosome
Kinetochore Fiber
Chromosome

16. The cell’s chromatin tightens.
Chapter 9
Cellular Reproduction
9.2 Mitosis and Cytokinesis
The Stages of Mitosis
Prophase
The cell’s chromatin tightens.
Sister chromatids are attached at the centromere.
Spindle fibers form in the cytoplasm.

17. The nuclear envelope seems to disappear.
Chapter 9
Cellular Reproduction
9.2 Mitosis and Cytokinesis
The nuclear envelope seems to disappear.
Spindle fibers attach to the sister chromatids.

18. Prophase
Spindle fibers called kinetochores attach to the centromere of each chromosome
Cytoplasm
Nucleolus
Nuclear Membrane
Chromosomes

19. Sketch on your paper

20. They line up in the middle of the cell.
Chapter 9
Cellular Reproduction
9.2 Mitosis and Cytokinesis
Metaphase
Sister chromatids are pulled along the spindle apparatus toward the center of the cell.
They line up in the middle of the cell.

21. Metaphase Asters at the poles Spindle Fibers
Chromosomes lined at the Equator

22. Chromosomes at Equator
Metaphase
Aster
Chromosomes at Equator

23. Sketch on your paper

24. The microtubules of the spindle apparatus begin to shorten.
Chapter 9
Cellular Reproduction
9.2 Mitosis and Cytokinesis
Anaphase
The microtubules of the spindle apparatus begin to shorten.
The sister chromatids separate.
The chromosomes move toward the poles of the cell.

25. Anaphase

26. Sketch on your paper

27. The chromosomes arrive at the poles and begin to relax.
Chapter 9
Cellular Reproduction
9.2 Mitosis and Cytokinesis
Telophase
The chromosomes arrive at the poles and begin to relax.
Two new nuclear membranes begin to form and the nucleoli reappear.
The spindle apparatus disassembles.

28. Sketch on your paper

29. In animal cells, microfilaments constrict, or pinch, the cytoplasm.
Chapter 9
Cellular Reproduction
9.2 Mitosis and Cytokinesis
Cytokinesis
In animal cells, microfilaments constrict, or pinch, the cytoplasm.
In plant cells, a new structure, called a cell plate, forms.

30. Cytokinesis

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

32. Division of Cytoplasm-cytokinesis
In plants- the cell plate forms down the equator of the cell
In animals-the cell pinches in along the equator

33. 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

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

35. Review of Mitosis

36. Name the Mitotic Stages:
Interphase
Name this?
Prophase
Telophase
Name this?
Metaphase
Anaphase

37. Summary

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

39. Name the Stages of Mitosis
Prophase
Anaphase
Metaphase
Interphase
Early Telophase,
Begin cytokinesis
Late Prophase
Telophase,
Advanced cytokinesis
Prophase
Anaphase

40. Telophase & Cytokinesis
Identify the Stages ?
Prophase ? ? ?
Metaphase
Anaphase
Prophase ? ? ?
Telophase & Cytokinesis
Anaphase
Telophase

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

42. Prokaryotic Cell Division
Binary Fission

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

44. Cell Division in Prokaryotes
Prokaryotes such as bacteria divide into 2 identical cells by the process of binary fission
Single chromosome makes a copy of itself
Cell wall forms between the chromosomes dividing the cell
Parent cell
Chromosome relicates
Cell splits
2 identical daughter cells

45. Prokaryotic Cell Undergoing Binary Fission

46. Animation of Binary Fission

47. Chemical signal telling the cell to divide
Chapter 9
Cellular Reproduction
9.3 Cell Cycle Regulation
Normal Cell Cycle
Cell regulator
Chemical signal telling the cell to divide

48. Abnormal Cell Cycle: Cancer
Chapter 9
Cellular Reproduction
9.3 Cell Cycle Regulation
Abnormal Cell Cycle: Cancer
Cancer is the uncontrolled growth and division of cells.
Cancer cells can kill an organism by crowding out normal
cells, resulting in the loss of tissue function.

49. Chapter 9
Cellular Reproduction
9.3 Cell Cycle Regulation
Causes of Cancer
The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations.
Various environmental factors can affect the occurrence of cancer cells.

50. Apoptosis Programmed cell death 9.3 Cell Cycle Regulation Chapter 9
Cellular Reproduction
9.3 Cell Cycle Regulation
Apoptosis
Programmed cell death

51. Chapter 9
Cellular Reproduction
9.3 Cell Cycle Regulation
Stem Cells
Unspecialized cells that can develop into specialized cells when under the right conditions

52. Chapter 9
Cellular Reproduction
9.3 Cell Cycle Regulation
Embryonic Stem Cells
After fertilization, the resulting mass of cells divides repeatedly until there are about –150 cells. These cells have not become specialized.

53. Chapter 9
Cellular Reproduction
9.3 Cell Cycle Regulation
Adult Stem Cells
Found in various tissues in the body and might be used to maintain and repair the same kind of tissue
Less controversial because the adult stem cells can be obtained with the consent of their donor

54. Mitosis is cell division in somatic (body) cells like skin or bone.
Meiosis is cell division in our sex cells (gametes- sperm & egg)

55. Meiosis 10.1

56. Facts About Meiosis
Daughter cells contain half the number of chromosomes as the original cell
Produces gametes (eggs & sperm)
Occurs in the testes in males (Spermatogenesis)
Occurs in the ovaries in females (Oogenesis)

57. Chromosome Number
EACH HUMAN BODY CELL CONTAINS 46 CHROMOSOMES, (2n) OR TWO COMPLETE SETS.
A CELL WITH ONLY ONE COMPLETE SET OF CHROMOSOMES IS CALLED A HAPLOID CELL. A Haploid Cell is abbreviated as 1n.

58. Chromosome Number cont’d…
GAMETES, (EGGS AND SPERM) CONTAIN ONLY ONE COMPLETE SET.  EACH HUMAN SPERM OR EGG (GAMETE) CONTAINS 23 CHROMOSOMES, THE HAPLOID NUMBER (1n) FOR ALL HUMANS.
WHEN AN EGG AND A SPERM JOIN THIS PROCESS IS CALLED FERTILIZATION.
THE SINGLE CELL THAT RESULTS FROM FERTILIZATION IS KNOWN AS A ZYGOTE.

59. Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Chromosomes
Homologous chromosomes—one of two paired chromosomes, one from each parent

60. Chromosomes and Chromosome Number
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Chromosomes and Chromosome Number
Same length
Same centromere position
Carry genes that control the same inherited traits

61. Compare diploid and haploid number
DIPLOID (2N)

62. Meiosis I The sexual life cycle in animals involves meiosis.
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
The sexual life
cycle in animals
involves meiosis.

63. Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Stages of Meiosis I
Reduces the chromosome number by half through the separation of homologous chromosomes
Involves two consecutive cell divisions called meiosis I and meiosis II

64. Meiosis Diploid (2N) Diploid (2N) Diploid (2N) Diploid (2N)
Haploid (1N)
Haploid (1N)

65. Chromosomes replicate.
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
Interphase
Chromosomes replicate.
Chromatin condenses.
Interphase

66. Pairing of homologous chromosomes occurs.
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
Prophase I
Pairing of homologous chromosomes occurs.
Each chromosome consists of two chromatids.
Prophase I
The nuclear envelope breaks down.
Spindles form.

67. Tetrads Form in Prophase I
Homologous chromosomes (each with sister chromatids)  
Join to form a TETRAD
Called Synapsis

68. Crossing over produces exchange of genetic information.
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
Prophase I
Crossing over produces exchange of genetic information.
Crossing over—chromosomal segments are exchanged between a pair of homologous chromosomes.
ADDS GENETIC DIVERSITY!!!!

69. Crossing-Over

70. Crossing-Over

71. Chromosome centromeres attach to spindle fibers.
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
Metaphase I
Chromosome centromeres attach to spindle fibers.
Metaphase I
Homologous chromosomes line up at the equator.

72. Metaphase I

73. Homologous chromosomes separate and move
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
Anaphase I
Homologous chromosomes separate and move
to opposite poles of the cell.
Anaphase I

74. Anaphase I

75. The spindles break down.
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis I
Telophase I
The spindles break down.
Telophase I
Chromosomes uncoil and form two nuclei.
The cell divides.

76. Telophase I
Meiosis I results in 2 haploid(1N) daughter cells, each with half the number of chromosomes as the original cell.

77. A second set of phases begins
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis II
Prophase II
A second set of phases begins
as the spindle apparatus forms and the
chromosomes condense.
Prophase II

78. Prophase II

79. A haploid number of chromosomes
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis II
Metaphase II
A haploid number of chromosomes
line up at the equator.
Metaphase II

80. Metaphase II

81. The sister chromatids are
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis II
Anaphase II
The sister chromatids are
pulled apart at the centromere by spindle
fibers and move toward the opposite poles
of the cell.
Anaphase II

82. Anaphase II

83. The chromosomes reach the poles, and
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis II
Telophase II
The chromosomes reach the poles, and
the nuclear membrane and nuclei reform.
Telophase II

84. Telophase II (includes cytokinesis)-
2 daughter cells divide into 4 new daughter cells, each new daughter cell has 23 chromosomes. (half the # of the original parent cell)
When gametes are joined in fertilization, diploid number is restored
Remember: you get half your chromosomes from your mother & half from your father

85. Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis II
Cytokinesis results in four haploid cells, each with n number of chromosomes.
Cytokinesis

86. The Importance of Meiosis
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
The Importance of Meiosis
Meiosis consists of 2 sets of divisions
Produces four haploid daughter cells that are not identical
Results in genetic variation

87. Meiosis Provides Variation
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Meiosis Provides Variation
Genetic variation also is produced during crossing over and during fertilization, when gametes randomly combine.

88. Sexual Reproduction v. Asexual Reproduction
Chapter 10
Sexual Reproduction and Genetics
10.1 Meiosis
Sexual Reproduction v. Asexual Reproduction
Asexual reproduction
The organism inherits all of its chromosomes from a single parent.
The new individual is genetically identical to its parent.
Sexual reproduction
Beneficial genes multiply faster over time.

89. Spermatogenesis Occurs in the testes
Men produce about 250,000,000 sperm per day

90. Spermatogenesis in the Testes
Spermatid

91. Oogenesis Occurs in the ovaries
Two divisions produce 3 polar bodies that die and 1 egg
Polar bodies die because of unequal division of cytoplasm
Immature egg called oocyte
Starting at puberty, one oocyte matures into an ovum (egg) every 28 days

92. Oogenesis in the Ovaries

93. Differences in meiosis
In males:
4 mature sperm
Males begin to produce sperm after puberty, produced constantly until death; meiosis II occurs immediately after meiosis I
Much smaller than egg
May have X or Y chromosomes
Have flagella to move
In females:
1 mature egg, 3 polar bodies which break down
Women born with all eggs they will have, meiosis I occurs before birth, meiosis II occurs once a month
Much larger
Have all X chromosomes
Has no method of movement

94. Meiosis/gamete production
Females have XX for last pair of chromosomes
Males have XY for last pair
Since all eggs are X, father determines the sex of the child since the sperm may be X or Y

95. Karyotyping
A map of the chromosomes that have been photographed through the microscope and then arranged according to a standard classification based on their group and size.
Boy XY
Girl XX

96. Cell Division Abnormalities
Non-disjunction failure of chromosome pairs to separate properly during cell division.
Example is Trisomy 21 or Down’s Syndrome

97. Trisomy 21 or Down’s Syndrome

98. Comparison of Divisions
Mitosis
Meiosis
Number of divisions 1 2
Number of daughter cells 4
Genetically identical?
Yes No
Chromosome #
Same as parent
Half of parent
Where
Somatic cells
Germ cells
When
Throughout life
At sexual maturity
Role
Growth and repair
Sexual reproduction

99. Video Clip
How cells divide: Mitosis vs. meiosis