1. Chapter 10: Cell Growth and Division Section 11.4: Meiosis
Cell Division
Chapter 10: Cell Growth and Division
Section 11.4: Meiosis

2. Do you remember any of the eight characteristics of living things?
Living things are based on a universal genetic code (DNA)
Living things grow and develop
Living things respond to their environment (stimulus)
Living things reproduce
Living things maintain a stable internal environment (homeostasis)
Living things obtain and use material and energy (metabolism)
Living things are made up of CELLS
Taken as a group, living things evolve over time

3. Plant vs. Animal Cell wall and cell membrane Large central vacuole
Chloroplast (photosynthesis) and mitochondria (cellular respiration)
Only a cell membrane
Smaller vacuoles
Only mitochondria (cellular respiration)
Lysosomes
Centrioles – used in cell division
Flagella

4. Chromatin and Chromosomes:
Inside the nucleus are fine strands of chromatin = a complex of DNA bound to protein
Chromatin coil up and become densely packed, forming chromosomes
Chromosomes are visible under a microscope when a cell divides

5. Number of chromosomes in a human body cell?
23 pairs of chromosomes = 46 chromosomes total
23 from mom and 23 from dad

6. Cells: Basic unit of structure and function in living things.
Cells with a specific structure and function and are found in multi-celled organisms.
Examples: skin cells, blood cells, brain cells, bone cells, liver cell, nerve cells, muscle cells, etc.
Brain cells
Blood cells
Liver cells

7. Where are chromosomes in eukaryotic cells?
CYTOPLASM
NUCLEUS

8. Two categories of cells
Prokaryotic
Eukaryotic
-Nucleus
-Unicellular
-No Nucleus
-Complex
-Cell wall (plants and bacteria)
-Membrane bound organelles
-Less complex
-Smaller Ribosomes less complex
-Cell membrane
-Multicellular
-DNA
- Ribosomes larger and complex
-Cytoplasm
-DNA is circular
-Ribosomes
-DNA is X shaped
-Living things
0.1-10µm
10-100µm

9. Vocabulary: Asexual Reproduction Sexual Reproduction Mitosis Meiosis
Diploid
Haploid
Chromatin
Chromatid
Centromere
Histone
Nucleosomes

10. Asexual Reproduction:
The production of genetically identical offspring from a single parent

11. Sexual Reproduction:
Offspring are produced by the fusion of two sex cells – one from each of two parents. These fuse into a single cell before the offspring can grow.

12. Mitosis: Division of the nucleus of a eukaryotic cell
Followed by cytokinesis –
division of the cytoplasm
The two daughter cells are
identical to the original cell

13. Meiosis:
Process that produces gametes from a diploid cell. A reductive division of the nucleus that produces four haploid gametes.

14. Diploid: Cells having two sets of chromosomes 2N = 46
Examples: All human body cells
Except reproductive cells (sperm and egg)

15. Haploid:
Cells containing only one set of chromosomes
N = 23

16. Chromatin:
DNA and protein (histones) in the nucleus of a non-dividing cell

17. Chromatid:
One of the two identical parts of a replicated chromosome

18. Centromere:
Point of attachment between sister chromatids

19. Histone:
Protein molecule that DNA wraps around during chromosome formation

20. Nucleosomes:
The beadlike structures formed by DNA and histone molecules

21. Cell Growth, Division, and Reproduction
Section 10.1

22. Bozeman Science - Why Are Cells Small
THINK ABOUT IT
When a living thing grows, what happens to its cells?
What are some of the difficulties a cell faces as it increases in size?
Bozeman Science - Why Are Cells Small

23. Limits to Cell Size Larger cells place more demands on their DNA
There are 2 main reasons why cells do not grow indefinitely:
Larger cells place more demands on their DNA
When a cell is small, the information stored in DNA is able to meet all of the cell’s needs
It’s like putting a Volvo engine in a Hummer… just doesn’t have the power to make it go.

24. Limits to Cell Size
2. Larger cells can’t move enough nutrients and waste across the cell membrane
Function of the cell membrane: help exchange materials between outside and inside of the cell.
A huge cell is going to need lots of food, water, and oxygen and produce lots of wastes that would have to travel through the cell and across the membrane.

25. Limits to Cell Size
The larger a cell becomes, the more demands the cell places on its DNA.
In addition, a larger cell is less efficient in moving nutrients and waste materials across its cell membrane.

26. Information “Overload”
Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access.
A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to serve the needs of the growing cell.

27. Exchanging Materials
Food, oxygen, and water enter a cell through the cell membrane. Waste products leave in the same way.
The rate at which this exchange takes place depends on the surface area of a cell.

28. Exchanging Materials
The rate at which food and oxygen are used up and waste products are produced depends on the cell’s volume.
The ratio of surface area to volume is key to understanding why cells must divide as they grow.

29. Ratio of Surface Area to Volume
Imagine a cell shaped like a cube...
As the length of the sides of a cube increases, its volume increases faster than its surface area, decreasing the ratio of surface area to volume.
If a cell gets too large, the surface area of the cell is not large enough to get enough oxygen and nutrients in and waste out.

30. Traffic Problems
To use the town analogy again, as the town grows, more and more traffic clogs the main street. It becomes difficult to get information across town and goods in and out.
Similarly, a cell that continues to grow would experience “traffic” problems. If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out.

31. Division of the Cell
Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division.
Before cell division, the cell copies all of its DNA.
It then divides into two “daughter” cells. Each daughter cell receives a complete set of DNA.
Cell division reduces cell volume. It also results in an increased ratio of surface area to volume, for each daughter cell.

32. Cell Division and Reproduction
Asexual Reproduction
Sexual Reproduction
A single parent
Genetically identical offspring
Prokaryotic and eukaryotic single-celled organisms and many multicellular organisms
Simple, efficient, & effective way for an organism to produce a large number of offspring.
Fusion of two sex cells – one from each of two parents
Genetically diverse offspring
Most animals and plants, and many single-celled organisms
Genetic diversity helps ensure survival of species when environment changes

33. The Process of Cell Division
Section 10.2
Cell Cycle and Mitosis (6:20)

34. Chromosomes
The genetic information that is passed on from one generation of cells to the next is carried by chromosomes.
Every cell must copy its genetic information before cell division begins.
Each daughter cell gets its own copy of that genetic information.
Cells of every organism have a specific number of chromosomes.

35. Prokaryotic Chromosomes
Prokaryotic cells lack nuclei. Instead, their DNA molecules are found in the cytoplasm.
Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains most of the cell’s genetic information.

36. Eukaryotic Chromosomes
In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin.
Chromatin is composed of DNA and histone proteins.
DNA coils around histone proteins to form nucleosomes.
The nucleosomes interact with one another to form coils and supercoils that make up chromosomes.

37. The Prokaryotic Cell Cycle
Binary fission is a form of asexual reproduction during which two genetically identical cells are produced.
For example, bacteria reproduce by binary fission.
Binary Fission (1:02)

38. The Eukaryotic Cell Cycle
The eukaryotic cell cycle consists of four phases: G1, S, G2, and M.
Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, and G2 phases. The M phase is the period of cell division.
Eukaryotic Cell Cycle | Biology | Genetics (4:19)

39. G1 Phase: Cell Growth
In the G1 phase, cells increase in size and synthesize new proteins and organelles.

40. G0 Phase Cells that leave the cell cycle Do NOT copy their DNA
Do NOT prepare for cell division
Example: cells of the central nervous system

41. S Phase: DNA Replication
In the S (or synthesis) phase, new DNA is synthesized when the chromosomes are replicated.

42. G2 Phase: Preparing for Cell Division
In the G2 phase, many of the organelles and molecules required for cell division are produced.
McGraw Hill Control of Cell Cycle
McGraw Hill - How the Cell Cycle Works

43. M Phase: Cell Division
In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis.
Mitosis is the division of the cell nucleus.
Cytokinesis is the division of the cytoplasm.
Eukaryotic Cell Cycle (3:45)
Mitosis (1:29)

44. Important Cell Structures Involved in Mitosis
Chromatid – each strand of a duplicated chromosome
Centromere – the area where each pair of chromatids is joined
Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle
Spindle – a fanlike microtubule structure that helps separate the chromatids

45. Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.
The centrioles move to opposite sides of nucleus and help organize the spindle.
The spindle forms and DNA strands attach at a point called their centromere.
The nucleolus disappears and nuclear envelope breaks down.
This is the longest stage of mitosis.

46. Metaphase
During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.
The spindle fibers connect the centromere of each chromosome to the two poles of the spindle.
This is the shortest phase of mitosis.

47. Anaphase
During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.
The chromosomes separate into two groups near the poles of the spindle.

48. Telophase Stages of Mitosis (30 s)
During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.
A nuclear envelope re-forms around each cluster of chromosomes.
The spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus.
Chromosomes uncoil.
Stages of Mitosis (30 s)

49. Cytokinesis Animal Cells Plant Cells
The cell membrane is drawn in (cleavage furrow)until the cytoplasm is pinched into two equal parts.
Each part contains its own nucleus and organelles.
In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall.
A cell plate forms between the divided nuclei that develops into cell membranes.
A cell wall then forms in between the two new membranes.
McGraw Hill - Mitosis and Cytokinesis Cytokinesis in Animal and Plant Cells (3 min)

50. The Stages of the Cell Cycle
Mitosis (6:10)

51. a) metaphase c) telophase e) interfase g) cytokinesis b) anaphase
d) prophase
f) anaphase

52. Video clips and Animations
Mitosis (1:29)
Eukaryotic Cell Cycle | Biology | Genetics (4:19)
Stages of Mitosis (4:30)
Mitosis (6:10)
Cell Cycle and Mitosis (6:20)
Meiosis (5:27)
PBS (Mitosis vs Meiosis) Interactive

55. Meiosis
Section 11.4

56. Important Vocabulary Meiosis Diploid Haploid Gamete
Sexual Reproduction

57. Chromosome Number
Chromosomes - strands of DNA and protein inside the cell nucleus - are the carriers of genes.
The genes are located in specific positions on chromosomes.
Meiosis (3:30)

58. Homologous Chromosomes
A body cell in an adult fruit fly has eight chromosomes, as shown in the figure.
Four of the chromosomes come from its male parent, and four come from its female parent.
These two sets of chromosomes are homologous, meaning that each of the four chromosomes from the male parent has a corresponding chromosome from the female parent.
Biology Meiosis (2:57)

59. Diploid Cells
A cell that contains both sets of homologous chromosomes is diploid, meaning “two sets.”
The diploid number of chromosomes is sometimes represented by the symbol 2N. 
For the fruit fly, the diploid number is 8, which can be written as 2N = 8, where N represents twice the number of chromosomes in a sperm or egg cell.

60. Haploid Cells
Some cells contain only a single set of chromosomes, and therefore a single set of genes.
Such cells are haploid, meaning “one set.”
The gametes of sexually reproducing organisms are haploid.
For fruit fly gametes, the haploid number is 4, which can be written as N = 4.

61. Zygote
Fertilized egg
Haploid sperm + Haploid egg = diploid zygote

62. Meiosis the Great Divide (7:40) Ameoba Sisters

63. Synapsis and Tetrads
During synapsis, the homologuous chromosomes pair up, forming a structure called a tetrad, which contains four chromatids.

64. Crossing Over
As homologous chromosomes pair up and form tetrads, they undergo a process called crossing-over.
First, the chromatids of the homologous chromosomes cross over one another.
Then, the crossed sections of the chromatids are exchanged.
Crossing-over is important because it produces new combinations of alleles in the cell.

65. Independent Assortment
Genes for different traits can segregate independently during the formation of gametes.
Biology Meiosis (2:57)

66. MEIOSIS I: Homologous chromosomes separate
INTERPHASE PROPHASE I METAPHASE I ANAPHASE I
Sister chromatids remain attached
centrioles
Sites of crossing over
Spindle Fibers
Nuclear envelope
Sister chromatids
Homologous chromosomes separate
Tetrad
Chromatin

67. TELOPHASE I AND CYTOKINESIS TELOPHASE II AND CYTOKINESIS
Meiosis II
PROPHASE II METAPHASE II ANAPHASE II
TELOPHASE I AND CYTOKINESIS
TELOPHASE II AND CYTOKINESIS
Cleavage furrow
Haploid daughter cells forming
Sister chromatids separate
MEIOSIS II: Sister chromatids separate
Animation of Meiosis (4 min)

68. Phases of Meiosis
Meiosis is a process in which the number of chromosomes per cell is cut in half through the separation of homologous chromosomes in a diploid cell.
Meiosis usually involves two distinct divisions, called meiosis I and meiosis II.
By the end of meiosis II, the diploid cell becomes four haploid cells.
Meiosis Square Dance Discovery Education (3:21)

69. Meiosis I: Interphase
Just prior to meiosis I, the cell undergoes a round of chromosome replication called interphase I.
Each replicated chromosome consists of two identical chromatids joined at the center.

70. Prophase I
The cells begin to divide, and the chromosomes pair up, forming a structure called a tetrad, which contains four chromatids.
As homologous chromosomes pair up and form tetrads, they undergo a process called crossing-over.

71. Metaphase I
During metaphase I of meiosis, paired homologous chromosomes line up across the center of the cell.

72. Anaphase I
During anaphase I, spindle fibers pull each homologous chromosome pair toward opposite ends of the cell.
When anaphase I is complete, the separated chromosomes cluster at opposite ends of the cell.

73. Telophase I
During telophase I, a nuclear membrane forms around each cluster of chromosomes.

74. Cytokinesis Cytokinesis follows telophase I, forming two new cells.
Meiosis (1:49)

75. Meiosis I Meiosis I results in two cells, called daughter cells.
Because each pair of homologous chromosomes was separated, neither daughter cell has the two complete sets of chromosomes that it would have in a diploid cell.
The two cells produced by meiosis I have sets of chromosomes and alleles that are different from each other and from the diploid cell that entered meiosis I.

76. Meiosis II
The two cells produced by meiosis I now enter a second meiotic division.
NOTE: Unlike the first division, neither cell goes through a round of chromosome replication before entering meiosis II.

77. Prophase II
As the cells enter prophase II, their chromosomes—each consisting of two chromatids—become visible.
The chromosomes do not pair to form tetrads, because the homologous pairs were already separated during meiosis I.

78. Metaphase II
During metaphase of meiosis II, chromosomes line up in the center of each cell.

79. Anaphase II
As the cell enters anaphase, the paired chromatids separate.

80. Telophase II The nuclear envelope reforms around the chromatids.
In the example shown here, each of the four daughter cells produced in meiosis II receives two chromatids.

81. Cytokinesis
These four daughter cells now contain the haploid number (N)—just two chromosomes each.
Meiosis: Crossing Overand Variability
Meiosis Square Dance (Full Version is 5:11)
This is repeated 2x in the video

82. Homologous chromosomes line up in the middle
Meiosis I
MEIOSIS I:
INTERPHASE PROPHASE I METAPHASE I ANAPHASE I
Chromatids remain attached
centrioles
Sites of crossing over
Spindle Fibers
Homologous chromosomes line up in the middle
Homologous chromosomes separate
Nuclear envelope
Sister chromatids
Tetrad
Chromatin

83. TELOPHASE I AND CYTOKINESIS TELOPHASE II AND CYTOKINESIS
Meiosis II
PROPHASE II METAPHASE II ANAPHASE II
TELOPHASE I AND CYTOKINESIS
TELOPHASE II AND CYTOKINESIS
MEIOSIS II: Sister chromatids separate
Cleavage furrow
Chromatids separate
4 Haploid daughter cells forming
Chromosomes line up
in the middle

84. Formation of Gametes Spermatogenesis Oogenesis Forms 4 haploid sperm
Forms 1 ovum (egg) and 3 polar bodies
Oogenesis (3:53)

85. Spermatogenisis