1. Chapter 10: Cell Growth and Division

2. The blue whale is the largest mammal in the world
The blue whale is the largest mammal in the world. The pygmy shrew is one of he smallest mammals in the world. How does the size of an average cell compare between the two?

3. A. the average cell of a blue whale is smaller then the average cell of a pygmy shrew. B. the average cell of a blue whale is larger then the average cell of a pygmy shrew. C. the average cell of a blue whale is about the same size as the average cell of a pygmy shrew.

4. Cell Growth
When an organism grows, the number of cells increase but the size of each cell remains small.

5. Limits to cell growth
DNA “overload”: The larger a cell becomes, the more demands the cell places on its DNA.
When a cell is small, DNA can easily control the cell’s functions and meet its needs.
When a cell is large, it still only has one copy of DNA, so it is more difficult for the cell to perform its functions.

6. Limits to cell growth Exchanging materials:
Large cells have more trouble moving substances across the cell membrane.
If a cell is too large, it is difficult to get enough oxygen and nutrients in and waste products out

7. Division of the Cell When a cell gets too large, it :
1. makes a copy of its DNA (replication),
and then…
2. divides to form two “daughter” cells.

9. Surface area to volume ratios6 1
1 X 1 X 1 cube SA:______ volume: _____
2 X 2 X 2 cube SA:______ volume: _____
10X10X10 cube SA:______ volume: _____
So when volume doubles, the surface area cannot “keep up” with it 8 24
600
1,000

10. Cell Division
Cell division in eukaryotes is more complex than in prokaryotes.
There are two stages of eukaryotic cell division
Mitosis: Division of the cell nucleus
Cytokinesis: Division of the cell cytoplasm

11. 3. Unicellular organisms reproduce asexually by mitosis or something similar to mitosis (prokaryotes cant do mitosis!)
a. The daughter cells are identical to the parents cells

12. Asexual Reproduction Is one cell reproducing by itself Two types:
Binary Fission: organism replicates its DNA and divides in half, producing two identical daughter cells
Example: bacteria
Budding: asexual process by which yeasts increase in number

13. Budding
Binary Fission

14. Chromosomes Chromosomes are made of condensed chromatin.
Chromatin consists of DNA and the proteins it is wrapped around.
The cells of every organism have a specific number of chromosomes
Ex. humans have 46 chromosomes

15. Chromatin v. chromosomes

16. Before cell division, each chromosome is replicated (meaning copied)
Chromosomes are only visible during cell division, when they are condensed. The rest of the time the chromatin is spread throughout the nucleus.
Before cell division, each chromosome is replicated (meaning copied)
When a chromosome is replicated, it consists of two identical “sister” chromatids.
When a cell divides the chromatids separate, and one goes to each of the two new cells.
Sister chromatids are attached to each other at the spot called the centromere.

17. 6. At the ends of each chromatid is an area called the telomere.
The telomere is filled with non-coding DNA
Like a protective cap
Gets shorter during each cell division
Shortening is believed to be linked to aging
Telomeres

19. The Cell Cycle
When a cell is NOT dividing, it is said to be in interphase.
The series of events that a cell goes through as it grows and divides is called the cell cycle.

21. Events of the cell cycle
Interphase, when the cell is NOT dividing, has three phases: G1, S, and G2.
 G1 phase: period of activity in which cells do most of their growing.
a.     Cells increase in size
b.     Cells synthesize (make) new proteins and organelles
S phase: DNA (chromosomes) is replicated
G2: organelles and molecules required for cell division are produced

23. M phase is the phase of cell division. This includes:
1. Mitosis, the division of the cell nucleus, which is made up of four segments including prophase, metaphase, anaphase, and telophase.
2. Cytokinesis, or the division of cytoplasm.

24. M phase
G2 phase
S phase
G1 phase

25. Mitosis
There are four phases in mitosis:
1.     Prophase
a. Longest phase in mitosis (take % of total time mitosis requires) b.     Chromosomes become visible because they are condensed

26. e. Nuclear envelope breaks down
c.    Centrioles become visible on opposite sides of the nucleus
i. The centrioles help organize the spindle, a structure made of microtubules that helps separate the chromosomes
ii. Chromosomes attach to the spindle fibers near the centromere
iii.      Plant cells to not have centrioles but do have mitotic spindles
d.     Nucleolus disappears
e.    Nuclear envelope breaks down

28. 2. Metaphase. a. Chromosomes line up in the center of. the cell. b
2. Metaphase a.     Chromosomes line up in the center of the cell b. Microtubules connect to the centromeres

29. 3. Anaphase
a.     Centomeres split and the sister chromatids separate b.     The sister chromatids become individual chromosomes
c.      Chromosomes move and separate into two groups
near the spindle d. Anaphase ends when the chromosomes stop moving

30. 4. Telophase
a. Chromosomes change form being condensed to dispersed b. A nuclear envelope forms around each cluster of chromosomes c.   Spindle breaks apart d. Nucleolus is visible in each daughter nucleus
Telophase in the midbodies of two daughter cells

31. Cytokinesis Mitosis occurs within the cytoplasm of one cell.
Cell division is complete when the cytoplasm divides.
In plants, a structure called the cell plate forms between the two daughter nuclei. The cell plate develops into a cell membrane and cell wall.

32. Cytokinesis
In animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into two equal parts. Each part has a nucleus and cytoplasmic organelles.
The cleavage of daughter cells is almost complete; this is visualized by microtubule staining

35. Interphase Cytokinesis Telophase
Centrioles
Chromatin
Interphase
Nuclear envelope
Cytokinesis
Nuclear envelope reforming
Telophase
Anaphase
Individual chromosomes
Metaphase
Centriole
Spindle
Chromosomes (paired chromatids)
Prophase
Centromere
Spindle forming

37. What are some reasons that cells undergo mitosis?
Growth
Repair
Maintenance
Asexual reproduction

38. Regulating the Cell Cycle Chapter 10-3
Different cell types divide at different rates.
Examples:
Muscle cells and nerve cells do not divide once they have developed.
Skin cells and cells in the bone marrow that make blood cells divide rapidly.

39. Proteins called Cyclins are present when the cell is dividing and are absent when the cell is not dividing.
They regulate the timing of the cell cycle

40. Controls on cell division
Cell growth and cell division can be turned on and off.
When you are injured your cells divide rapidly to repair the injury. When the injury has healed, the cells stop dividing.

41. Uncontrolled cell growth
When cells in your body CANNOT control cell growth and division, cancer may form.
Cancer cells cannot respond to the signals that regulate the division of cells.
When cancer cells have been dividing uncontrollably, tumors form.
Tumors can damage surrounding tissue.
Cells from tumors can break free and travel to other parts of the body, forming new tumors.

42. Regulating Cell Divisions
Internal regulators – Signals from within the cell to regulate the cell cycle.
They make sure everything is complete before moving on.

43. Regulating Cell Divisions
External regulators – Stimulate or suppress cell growth by recognizing the surrounding situation.
Injury repair
Embryonic stem cell differentiation

44. Cancer Cancer cells tend to have a damaged oncogene.
This gene possess the information needed to respond to internal and external regulators.

45. During the Reading Metastasis : Benign: 3. Malignant:
Define the following
Metastasis :
Benign:
3. Malignant:
The process or condition of abnormal cell migration and tissue invasion.
Cells that stay where they are usually considered as a Tumor. (Not Cancer)
Cells can break off and infect other areas of the body (Cancer)

47. There are several reasons that cells may lose the ability to control growth.
Examples:
1. smoking
2. radiation exposure
3. viral infection
Scientists who study cancer are researching how cells divide.

48. Reviewing Mitosis

49. When does the following occur?
(Name the phase of the cell cycle. If it is in mitosis, name the phase of mitosis)
1. Sister chromatids separate.
2. Chromosomes line up across the center of the cell.
3. The cell’s DNA molecules are copied.
4. The cytoplasm pinches in half.
5. A spindle forms.
Mitosis - Anaphase
Mitosis - Metaphase
S Phase
Cytokinesis
Mitosis - Prophase

50. What are the structures shown
What are the structures shown? How many copies of the cell’s DNA are shown here?
A. Sister chromatids
B. Centromere 2

51. Interphase ? Phase Mitosis Cytokinesis ? ? ? ? Cell Cycle M Phase
Prophase
Metaphase
Anaphase
Telophase

52. What is the name of the structure labeled:
Centriole
Chromosome
Spindle fiber

53. If your were to examine a sample of 1000 cells undergoing mitosis, in which of the phases listed below would you expect to find most of the cells?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase

54. Meiosis (Gametogenesis) Chapter 11-4

55. Chromosomes
You have 23 different pairs of chromosomes, for a total of 46 chromosomes.
One chromosome in each pair came from your mother and one from your father.

57. Each chromosome in a pair is said to be homologous, meaning that the chromosome from the father has a corresponding chromosome from the mother.

58. Cells that contain both sets of homologous chromosomes are called diploid (2N).
All of your cells except the sex cells (sperm and eggs; also called gametes) are diploid (2N).
Gametes are haploid (N), meaning they contain only one copy of each chromosome.
When one sperm and one egg combine their DNA, there are two versions of each chromosome.

59. haploid
haploid
diploid

60. We use “N” to represent the haploid number of chromosomes and “2N” to represent the diploid number of chromosomes.
1. For humans, the haploid number is We write this as N = 23. The diploid number is 46, which we write as 2N = 46.
2. In fruit flies, N = 4 and 2N = 8.

61. In fruit flies, N (______) = 4 and
Practice with haploid and diploid:
In fruit flies, N (______) = 4 and
2N (______) = ___
haploid
diploid 8.
If elephants have a diploid number of 56, what is their haploid number? 28

62. Meiosis
Meiosis is the process that divides one diploid (2N) cell to form four haploid (N) cells.
This process is a reductional division because the number of chromosomes per cell are cut in half.
Meiosis is how gametes are formed.

63. There are two divisions that occur in meiosis: Meiosis I and Meiosis II.
1. Before meiosis I begins, cells go through Interphase I.
2. This involves DNA replication, forming a duplicate copy of each chromosome.
3. Each chromosome is made of two sister chromatids.
centrioles
Nucleus with duplicated DNA that is not condensed.
cell

64. Meiosis I is similar to mitosis. a. Prophase I:
i.      Centrioles are visible on opposite sides of the nucleus
ii.      Nucleolus disappears
iii.      Nuclear envelope breaks down
spindle
centrioles
DNA condensed as chromosomes

65. iv. Homologous chromosomes pair
1. When a pair of chromosomes aligns a tetrad is formed.
2.      When chromosomes form a tetrad, they exchange portions of their chromatids in a process called crossing-over.
3. Crossing-over produces new combinations of DNA.
tetrad

66. b.     Metaphase I:
i.      Spindle fibers attach to the chromosomes at the centromere
spindle
centromere
centrioles
chromosomes (DNA)

67. c.     Anaphase I:
i. Spindle fibers pull the homologous chromosomes toward opposite ends of the cell.
ii. Chromosomes move and separate into two groups near the spindle
iii. Anaphase ends when the chromosomes stop moving
spindle
chromosomes
(DNA)
centrioles

68. d. Telophase I e. Cytokinesis i. Cytoplasm divides centrioles
i.      Nuclear membranes form around chromosomes
ii.      Daughter nuclei form
e. Cytokinesis
i. Cytoplasm divides
Nucleus
centrioles
chromosomes
(DNA)
Nucleus

69. Meiosis I produces two haploid (N) daughter cells that have only one copy of each chromosome. Each chromosome is made of two sister chromatids.

71. Meiosis II After Meiosis I, cells enter Meiosis II.
No DNA replication occurs between Meiosis I and Meiosis II.
Meiosis II separates the sister chromatids.

72. i. Centrioles are visible on opposite sides of the nucleus
a.     Prophase II:
i. Centrioles are visible on opposite sides of the nucleus
ii. Nucleolus disappears
iii. Nuclear envelope breaks down
chromosome

73. i. Chromosomes align like they do in mitosis
b.     Metaphase II:
i. Chromosomes align like they do in mitosis
ii. Chromosomes are attached to the spindle at the centromere.
centrioles
spindle
chromosome

74. Sister chromatids separate and move towards opposite ends of the cell.
Anaphase II:
Sister chromatids separate and move towards opposite ends of the cell.
centrioles
spindle
chromosome

75. f. Meiosis II - produces four haploid (N) daughter cells
d. Telophase II:
i. Nuclear membranes form around chromosomes
ii. Daughter nuclei form
e.  Cytokinesis:
i. Division of the cytoplasm
f.  Meiosis II - produces four haploid (N) daughter cells
centrioles
nucleus
chromosome

76. Gamete formation
In male animals, the haploid gametes are called sperm.
In female animals, the haploid gametes are called eggs.

77. When the male and female gametes join, this is called fertilization and a zygote is formed.

78. Comparing mitosis and meiosis
Mitosis produces two genetically identical diploid (2N) somatic (body) cells. Mitosis allows an organism’s body to grow and to replace cells. In organisms that reproduce asexually, new organisms are produced by mitosis.
Meiosis (or gametogenesis) produces four genetically different haploid (N) cells. Meiosis produces gametes for use in sexual reproduction.