1. DNA Synthesis, Mitosis, and Meiosis
Chapter 5
Cancer
DNA Synthesis, Mitosis, and Meiosis
Figure 5.2

2. 5.1
Chapter 5 Section 1
What Is Cancer?
Figure 5.2

3. Potentially cancerous cell
5.1 What Is Cancer?
What Is Cancer?
Unregulated cell division
Tumor: mass of cells with no function
Malignant if tumor invades surrounding tissue (cancerous)
Tumor
Metastatic if individual cells break away and start a new tumor elsewhere (cancerous)
Normal cell
Potentially cancerous cell
Benign if tumor has no effect on surrounding tissue (noncancerous)
Normal cell division
Unregulated cell division
Figure 5.2

4. Potentially cancerous cell
5.1 What Is Cancer?
Benign tumor: doesn’t affect surrounding tissues
Malignant tumor: invades surrounding tissues; cancerous
Metastasis: cells break away from a malignant tumor and start a new cancer at another location
Benign if tumor has no effect on surrounding tissue (noncancerous)
Metastatic if individual cells break away and start a new tumor elsewhere (cancerous)
Malignant if tumor invades surrounding tissue (cancerous)
Normal cell division
Unregulated cell division
Tumor
Potentially cancerous cell
Normal cell
Figure 5.2

5. 5.1 What Is Cancer? Metastatic cells
Metastatic cells can travel throughout the body via the circulatory system or the lymphatic system.
Lymphatic system collects fluid that leaks from capillaries.
Lymph nodes filter the lymph.
Cancer cells found in lymph nodes indicate metastasis has taken place.

6. 5.1 What Is Cancer? Cancer cells differ from normal cells:
Divide when they shouldn’t
Invade surrounding tissues
Move to other locations in the body

7. 5.1 What Is Cancer?
Risk factors: increase a person’s risk of developing a disease
Tobacco use: tobacco contains many carcinogens (chemicals that can cause cancer)
Alcohol consumption: alcohol and tobacco increase risk in multiplicative manner
High-fat, low-fiber diet

8. 5.1 What Is Cancer? - Risk factors
Risk factors continued
Lack of exercise increases risk in two ways
Exercise keeps immune system healthy
Exercise helps prevent obesity
Increasing age
Immune system declines with age
Cumulative damage from carcinogens
Cells that divide frequently

9. 5.1
End of Chapter 5 Section 1
What Is Cancer?
Figure 5.2

10. Passing Genes and Chromosomes to Daughter Cells
5.2
Chapter 5 Section 2
Passing Genes and Chromosomes to Daughter Cells
Figure 5.2

11. 5.2 Passing Genes and Chromosomes to Daughter Cells
Asexual reproduction:
Only one parent
Offspring are genetically identical to parent
Sexual reproduction
Gametes are combined from two parents
Offspring are genetically different from one another and from the parents

12. 5.2 Passing Genes and Chromosomes to Daughter Cells
Before dividing, cells must copy their DNA
Gene: section of DNA that has the instructions for making one protein
One molecule of DNA is wrapped around proteins to form a chromosome containing hundreds of genes.
Different species have different numbers of chromosomes (we have 46).

13. 5.2 Passing Genes and Chromosomes to Daughter Cells
Chromosomes are uncondensed before cell division
They are duplicated through DNA replication
Duplicated chromosomes, held together at the centromere, are called sister chromatids
Unduplicated chromosome
Duplicated chromosome A b C
Sister chromatids
Centromere
Replication
Figure 5.6

14. 5.2 Passing Genes and Chromosomes to Daughter Cells
(a) DNA replication
New strands
Parental strands
DNA Replication
DNA molecule is split up the middle of the helix
Nucleotides are added to each side
Result is two identical daughter molecules, each with one parental strand and one new strand (semiconservative replication)
Figure 5.5a

15. 5.2 Passing Genes and Chromosomes to Daughter Cells
DNA polymerase: the enzyme that replicates DNA
Forms covalent bonds between nucleotides on the new strands
Forms hydrogen bond between nitrogenous bases
(b) The DNA polymerase enzyme facilitates replication.
Unwound DNA helix
Free nucleotides
DNA polymerase
Figure 5.5b

16. 5.2 Passing Genes and Chromosomes to Daughter Cells
PLAY
Animation—The Structure of DNA

17. Passing Genes and Chromosomes to Daughter Cells
5.2
End of Chapter 5 Section 2
Passing Genes and Chromosomes to Daughter Cells
Figure 5.2

18. The Cell Cycle and Mitosis
5.3
Chapter 5 Section 3
The Cell Cycle and Mitosis
Figure 5.2

19. 5.3 The Cell Cycle and Mitosis
Cell cycle: the “lifecycle” of the cell
Three steps:
Interphase: the DNA replicates
Mitosis: the copied chromosomes are moved into daughter cells
Cytokinesis: the cell is split into 2 daughter cells

20. 5.3 The Cell Cycle and Mitosis - Interphase
Interphase has three phases:
G1: cell grows, organelles duplicate
S: DNA replicates
G2: cell makes proteins needed to complete mitosis
Most of the cell cycle

21. 5.3 The Cell Cycle and Mitosis - Mitosis
Produces genetically-identical daughter cells
Sister chromatids are pulled apart
Four stages:
Prophase
Metaphase
Anaphase
Telophase

22. 5.3 The Cell Cycle and Mitosis - Mitosis
Prophase: cell prepares for division
Replicated chromosomes condense
Nuclear envelope disappears
Microtubules pull the chromosomes toward the middle of the cell
In Animal cells, microtubules are attached to centrosomes at the poles of the cell

23. 5.3 The Cell Cycle and Mitosis - Mitosis
Metaphase: chromosomes prepare for separation
chromosomes are aligned across the middle of the cell

24. 5.3 The Cell Cycle and Mitosis - Mitosis
Anaphase: chromotids separate
centromeres split,
sister chromatids are pulled apart toward opposite poles

25. 5.3 The Cell Cycle and Mitosis - Mitosis
Telophase: cells finalize nuclear division
Nuclear envelopes reform around chromosomes
Chromosomes revert to uncondensed form

26. 5.3 The Cell Cycle and Mitosis
PLAY
Animation—Mitosis

27. 5.3 The Cell Cycle and Mitosis - Cytokinesis
Stage in which two daughter cells are formed from the original one
In Plants, a new cell wall forms between the cells, built from cellulose

28. 5.3 The Cell Cycle and Mitosis - Cytokinesis
Animals:
Don’t have a cell wall
Proteins pinch the original cell into two new cells
After cytokinesis, cells reenter interphase.

29. 5.3 The Cell Cycle and Mitosis

30. The Cell Cycle and Mitosis
5.3
End of Chapter 5 Section 3
The Cell Cycle and Mitosis
Figure 5.2

31. Cell Cycle Control and Mutation
5.4
Chapter 5 Section 4
Cell Cycle Control and Mutation
Figure 5.2

32. 5.4 Cell Cycle Control and Mutation
Control of the Cell Cycle
Cell division is a tightly controlled process
Normal cells halt at checkpoints
Proteins survey the condition of the cell
Cell must pass the survey to proceed with cell division

33. 5.4 Cell Cycle Control and Mutation
3 checkpoints during the cell cycle
G1 checkpoint: are growth factors present?
Cell must also be large enough and have enough nutrients
G2 checkpoint: has DNA replicated properly?
Metaphase checkpoint: have all chromosomes attached properly to microtubules?

34. 5.4 Cell Cycle Control
PLAY
Animation—The Cell Cycle

35. 5.4 Cell Cycle Control and Mutation
Cell Cycle Control and Cancer
Two important genes
Proto-oncogenes
Tumor-suppressor genes

36. 5.4 Cell Cycle Control and Mutation
Proto-oncogenes
Proto-oncogenes are genes that code for the cell cycle control proteins
Many proto-oncogenes encode for growth factors
Mutation: a change in the sequence of DNA
This changes the structure and function of the protein
Mutations may be inherited or caused by carcinogens

37. 5.4 Cell Cycle Control and Mutation
Oncogenes
When proto-oncogenes mutate, they become oncogenes
Their proteins no longer properly regulate cell division
They usually over stimulate cell division
(a) Mutations to proto-oncogenes
Functional protein stimulates cell division only when conditions are right.
Mutated protein may overstimulate cell division by overriding checkpoint control.
Mutation
Protein
DNA
Proto-oncogene
Mutated proto-oncogene (oncogene)
Figure 5.12a

38. 5.4 Cell Cycle Control and Mutation
Tumor suppressor genes: genes for proteins that stop cell division if conditions are not favorable
When mutated, can allow cells to override checkpoints
(b) Mutations to tumor-suppressor genes
Tumor-suppressor protein stops tumor formation by suppressing cell division.
Mutated tumor -suppressor protein fails to stop tumor growth.
Mutation
Protein
DNA
Tumor suppressor
Mutated tumor suppressor
Figure 5.12b

39. 5.4 Cell Cycle Control and Mutation –
Many Mutations Are Required for Cancer to Develop
Angiogenesis: tumor gets its own blood supply
Loss of contact inhibition: cells will now pile up on each other

40. 5.4 Cell Cycle Control and Mutation –
Many Mutations Are Required for Cancer to Develop
Loss of anchorage dependence: enables a cancer cell to move to another location
Immortalized: cells no longer have a fixed number of cell divisions

41. 5.4 Cell Cycle Control and Mutation – Many Mutations Are Required for Cancer to Develop
Multiple hit model: process of cancer development requires multiple mutations
Some mutations may be inherited (familial risk)
Most are probably acquired during a person’s lifetime

42. Cell Cycle Control and Mutation
5.4
End of Chapter 5 Section 4
Cell Cycle Control and Mutation
Figure 5.2

43. Cancer Detection and Treatment
5.5
Chapter 5 Section 5
Cancer Detection and Treatment
Figure 5.2

44. 5.5 Cancer Detection and Treatment
Early detection and treatment is best
Different detection methods for different cancers
Some cancers produce increased amount of a characteristic protein
Biopsies

45. 5.5 Cancer Detection and Treatment
Biopsy: surgical removal of cells or fluid for analysis
Needle biopsy: removal is made using a needle
Laparoscope: surgical instrument with a light, camera, and small scalpel

46. 5.5 Cancer Detection and Treatment -
Treatment Methods
Chemotherapy: drugs that selectively kill dividing cells
Combination of different drugs used (“cocktail”)
Interrupt cell division in different ways
Helps prevent resistance to the drugs from arising
Normal dividing cells are also killed (hair follicles, bone marrow, stomach lining)

47. 5.5 Cancer Detection and Treatment - Treatment Methods
Radiation therapy: use of high-energy particles to destroy cancer cells
Damages their DNA so they can’t continue to divide or grow
Usually used on cancers close to the surface
Typically performed after surgical removal of tumor

48. Cancer Detection and Treatment
5.5
End of Chapter 5 Section 5
Cancer Detection and Treatment
Figure 5.2

49. Meiosis – cell division for reproduction
5.6
Chapter 5 Section 6
Meiosis – cell division for reproduction
Figure 5.2

50. 5.6 Meiosis Chromosomes of Somatic Cells Humans have 46 chromosomes
Chromosomes come in homologous pairs
Diploid – cells have a pair of each chromosome
22 pairs of autosomes
1 pair of sex chromosomes

51. 5.6 Meiosis Homologous pairs of chromosomes carry the same genes.
Alleles
But each chromosomes may carry a different version of the gene, called alleles
Alleles code for a different version of the same protein
Figure 5.22

52. 5.6 Meiosis
Meiosis
Specialized form of cell division in gonads to produce gametes
Meiosis reduces number of chromosomes in each cell by one-half
Gamete gets one of each pair
Somatic cells are diploid (2n), but gametes are haploid (1n)
Eggs and sperm fuse to form diploid Zygote

53. 5.6 Meiosis Chromosome Replicaton
Before meiosis can occur, DNA is duplicated
DNA is duplicated in the S phase
Creates 2 sister chromotids
Held together by centromere
Figure 5.22

54. Interphase and Meiosis
Cell division that reduces diploid to haploid
Meiosis takes place in two stages: meiosis I and meiosis II G1 S
Cell growth and preparation for division
End of previous mitotic event
S and G phases similar to the S and G phases of mitosis
Interphase and Meiosis
Cell growth
Interphase (G1, S, G2)
DNA is copied G2
Figure 5.22

55. 5.6 Meiosis Steps of Meiosis
Meiosis I separates the members of a homologous pair from each other.
After meiosis I, the resulting cells are haploid (n)
Meiosis I is therefore called ‘reduction division’
Meiosis II is essentially like mitosis; it separates the sister chromatids

56. 5.6 Meiosis Four Steps of Meiosis I
Meiosis I separates the members of a homologous pair from each other.
During prophase I there may be crossing over between members of homologous pairs

57. 5.6 Meiosis Four Steps of Meiosis I Metaphase I
homologous pairs line up at the equator of cell
Microtubules attach to centromere

58. 5.6 Meiosis Four Steps of Meiosis I Anaphase I
Homologous pairs are separated by shortening microtubules
Telophase I – nuclear envelop reforms

59. 5.6 Meiosis
Meiosis II
Consists of Prophase II, Metaphase II, Anaphase II, and Telophase II
Virtually identical to mitosis
Sister chromatids are separated

60. 5.6 Meiosis
Two events create millions of different gametes from each parent
Crossing over during prophase I
Random alignment during metaphase I
> Both increase the variation of next generation

61. 5.6 Meiosis Crossing over during prophase I
exchange of equivalent portions of chromosomes between members of a homologous pair
Results in new assortment of genes in gametes

62. 5.6 Meiosis Random Assortment during metaphase I
Homologous pairs of chromosomes arrange arbitrarily at cell equator
Results in new assortment of genes in gametes

63. 5.6 Meiosis
Meiosis

64. 5.6 Meiosis - Mistakes in Meiosis
Nondisjunction: failure of homologues to separate normally during meiosis
Results in a gamete having one too many chromosomes (trisomy) or one too few chromosomes (monosomy)

65. 5.6 Meiosis - Mistakes in Meiosis
Human Nondisjunction of autosomes

66. 5.6 Meiosis - Mistakes in Meiosis
Human Nondisjunction of sex chromosomes

67. 5.6 Meiosis Inheriting Cancer
For cancer mutations to be passed on to offspring, they must occur in cells that give rise to gametes.
Mutations in somatic cells (e.g., skin cancer) are not heritable.

68. Comparison of Mitosis & Meiosis – Fig 5.27

69. Meiosis – cell division for reproduction
5.6
End of Chapter 5 Section 6
Meiosis – cell division for reproduction
Figure 5.2

70. 5.6
End of Chapter 5
Figure 5.2