1. Bellwork
Domestic horses have 64 chromosomes. How many chromosomes should be in an egg cell of a female horse? A. 16 B. 32 C. 64 D. 128

2. Bellwork
In a sample of double-stranded DNA, 30% of the nitrogenous bases are thymine. What percentage of the nitrogenous bases in the sample are adenine?
20%
70%
30%
40%

3. Agenda 5/3- Cell Cycle, Division (Mitosis)
Bellwork
New Information: Cell Cycle, Mitosis
Virtual Lab- Identifying Stages of the Cell Cycle

4. Cell Cycle and Cell Division (Mitosis)
What is mitosis? Why is it important?

5. Cell Division 3 reasons for mitotic cell division (mitosis):
Growth
Repair
Replacement
Parent cell divides into two identical daughter cells

6. Cell Division
Cells divide to make new cells- DNA is replicated so each daughter cell gets an exact copy.
DNA condenses into chromosomes during mitosis. 6

7. Cell Division Humans have 46 chromosomes, 23 from each parent.
Haploid cells: only one of each chromosome (n)
Diploid cells: two of each chromosome (2n)

8. Cell Cycle (click for video clip)
G1 phase
M phase
S phase
G2 phase

9. Interphase- longest G1 Phase Cell growth S Phase DNA replication
preparation for mitosis
M Phase
mitosis and cytokinesis
Allium G1
M phase S G2

10. Interphase Nucleus and nuclear envelope are visible.
One or more nucleoli are visible.
The rest of the nucleus is filled with chromatin.

11. Figure 10-5 Prophase Interphase Cytokinesis Metaphase Telophase
Anaphase

12. Prophase pro- = first; first stage of mitosis
Nuclear envelope breaks down
Chromatin condenses into chromosomes
Centrioles move to opposite poles of the cell
Spindle fibers attach to chromosomes at the centromere.
(plant cells have microtubule organizing centers instead of centrioles)

13. Metaphase Chromosome line up in the Middle of the cell
Chromosome centromeres are attached to the spindle at the poles of the cell

14. Anaphase
Chromosome centromeres separate and sister chromatids move Apart to the opposite ends of the cell

15. Telophase Chromosomes precipitate back into strands of DNA (chromatin)
A new nuclear envelope begins to form around each of the two new clumps of DNA

16. Cytokinesis Same time as Telophase Animal Cells:
(“cell splitting”)
Same time as Telophase
Animal Cells:
cytoplasm splits as the cell membrane draws inward (cleavage furrow) and splits the cell in two
Plant Cells:
cytoplasm splits as a cell plate forms between the two new nuclei, then a new cell membrane

17. Cell Cycle and Mitosis I P M A T C I Protect Mothers And Their
Children
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

18. Cell Cycle and Mitosis Virtual Lab
Go to
Make a table like the one you’ll see before the activity begins.
Answer the following questions:
Which phase of the cell cycle is longest? How do you know? Which is shortest, and how do you know?

19. Bellwork 5/4 What are the 4 phases of the cell cycle?
What are the 4 phases of mitosis?
What phases are shown below?

20. Agenda 5/4- Cell Cycle and Cancer
Bellwork
Notes- Cell Cycle Control and Cancer
Lab- Mitosis in Onion Root Tip Cells
HW- finish lab questions, study for test (Fri)- DNA structure and replication, cell cycle, and mitosis

21. Binary Fission
Prokaryotes (bacteria) reproduce by a type of cell division called binary fission.
In binary fission the single bacterial chromosome replicates and the two daughter chromosomes actively move apart.

22. G1 phase
M phase
S phase
G2 phase

23. The Cell Cycle Control System
The events of the cell cycle are directed by a cell cycle control system, similar to a clock.
Figure 12.14
Control system
G2 checkpoint
M checkpoint
G1 checkpoint G1 S G2 M

24. The Cell Cycle Control System
There are specific checkpoints where the cell cycle stops until a go-ahead signal is received.
G1 checkpoint G1 G0
(a) If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.
(b) If a cell does not receive a go-ahead signal at the G1checkpoint, the cell exits the cell cycle and goes into G0, a non-dividing state.
Figure A, B

25. Control of Cell Division
In density-dependent inhibition crowded cells stop dividing.
Most animal cells also exhibit anchorage dependence in which they must be attached to a substratum to divide.
Cells anchor to dish surface and
divide (anchorage dependence).
When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition).
Normal mammalian cells. The availability of nutrients, growth factors, and a substratum for attachment limits cell density to a single layer.
(a)
25 µm
Figure A

26. Control of Cell Division
Cancer cells: no density-dependent inhibition or anchorage dependence.
Do not respond normally to the body’s control mechanisms and form tumors.
Loss of the cell cycle controls.
25 µm
Cancer cells do not exhibit anchorage dependence or density-dependent inhibition.
Cancer cells. Cancer cells usually continue to divide well beyond a single layer, forming a clump of overlapping cells.
(b)
Figure B

27. Control of Cell Division
Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body where they may form secondary tumors.

28. Cancer Risk Factors Quiz

29. Lab Objectives
To list the phases of the cell cycle in the order in which they occur.
To list the phases of the M-phase of the cell cycle (Mitosis) and explain what happens during each.
To illustrate/draw what happens during each phase of Mitosis.
To identify the role of cell structures during cell division (centrioles, chromatin, chromosomes, nucleus).
To learn the importance of cell division for organisms (asexual reproduction, growth, repair).

30. Mitosis in Allium Root
Interphase
Prophase
Metaphase

31. Mitosis in Allium Root
Anaphase
Telophase

33. Prophase
Interphase
Metaphase
Telophase
Anaphase

35. Allium Lab- Mitosis X = the area just behind the root cap
Y = the area behind region X (fewer cells, fewer nuclei visible) Y X

36. Bellwork 5/6 Identify one function of mitosis.
The illustration below represents a cell that is
entering mitosis.
Identify one function of mitosis.
The cell shown in the illustration has recently completed the synthesis phase (S phase) of the cell cycle and is in prophase of mitosis.
2. What happened in this cell during the S phase in preparation for division? Describe the evidence that supports your answer.
3. In your Student Answer Booklet, draw the end products that will be formed when this cell completes mitosis.

37. Agenda 5/6- Mitotic Cell Division
Bellwork
Discuss lab, start lab report
Review for Monday’s test

38. Agenda 5/9- Sexual vs. Asexual Reproduction
Cell Cycle, Mitosis, and DNA Replication Test
New information: Sexual vs. Asexual Reproduction
Video- Life’s Greatest Miracle
HW-
Due Tues: Lab Report
Due Wed: Vocabulary (on next slide)

40. HW- vocabulary- use book or internet to define these terms (max 7 words per definition, in your OWN WORDS) and draw a picture for each.
Homologous chromosomes
Tetrad
Crossing over
Trait
Gene
Allele
Hybrid
Homozygous
Heterozygous
Phenotype
Genotype
Probability

42. Eukaryotic Cell Division
Mitosis- normal cell division
Parent cell divides into two identical daughter cells (diploid = 2n)
n = number of types of chromosomes
Meiosis- cell division resulting in reproductive cells (gametes)
Parent cell divides into 4 daughter cells, each with half the number of chromosomes (haploid = 1n)

43. Mitosis
2 diploid daughter cells formed, just like parent cell (two of each chromosome)
Preceded by interphase (G1, S, G2 phase)
Mitosis:
Prophase
Metaphase
Anaphase
Telophase

44. Figure 10-5 Prophase Interphase Cytokinesis Metaphase Telophase
Anaphase

45. Why don’t you look exactly like your parents or siblings?
A different form of cell division: Meiosis!
Sexual reproduction increases genetic variation in a population, which increases a species’ ability to adapt to changes in their environment.

46. Sexual Reproduction
Male gamete (sperm) and female gamete (egg) are haploid (1n)
Fertilization occurs when an egg and a sperm fuse to form a zygote (2n).
Meiosis is the form of cell division that results in gametes.

47. Meiosis occurs in somatic (body) cells to produce reproductive cells (gametes)
4 haploid daughter cells formed (only one of each chromosome)
Preceded by interphase and DNA replication
Two Divisions:
Meiosis I
Meiosis II

48. Bellwork 5/10

49. Agenda 5/10- Sexual vs Asexual Reproduction
Bellwork
New Information: Sexual vs. Asexual Reproduction
Video- finish and discuss
HW- vocabulary

50. Why Sex? The Evolution of Sexual Reproduction
offspring are a combination of parents
introduces variety in population
Asexual Reproduction
offspring are identical to parents
little variety in population
binary fission, budding

51. The Evolution of Sexual Reproduction

52. The Red Queen Hypothesis (start at 3:00 min) The Evolution of Sexual Reproduction
The leading hypothesis for why sexual reproduction has persisted
Refers to Lewis Carroll’s Through the Looking Glass
The Red Queen says to Alice:
“It takes all the running you can do, to stay in the same place.”

53. The Red Queen Hypothesis The Evolution of Sexual Reproduction
As species that live at each other's expense co-evolve, they are engaged in a constant evolutionary struggle for a survival advantage. They need "all the running they can do" because the landscape around them is constantly changing. (predator/prey, disease/host)
In other words, hosts change the locks, and parasites, etc invent new keys.
Sexual reproduction is necessary to fight disease, avoid predation, get food, etc.

54. Why Sex? Advantages and Disadvantages of Asexual Reproduction
Pass on all of your genes
No mating behavior costs (don’t have to spend time or energy looking for a mate, no energy wasted on showy displays)
Disadvantages:
Little or no variation
More susceptible to parasites, viruses, etc.
Sexual Reproduction
Advantages:
Variation
More rapid rate of adaptation in a changing environment
Disadvantages:
Costs of mating behavior: competition, no mating
Only pass on half your genes

55. Costs of Sexual Reproduction: Displays, Competition for Mates

56. Life’s Greatest Miracle
Video with worksheet.
Answer all questions- classwork grade.

57. Life’s Greatest Miracle
Video link
Answer the questions on the worksheet

58. Bellwork 5/11

59. Agenda 5/11- Meiosis Bellwork
New Information: Meiotic Cell Division (Meiosis)
Activities:
Modeling Crossing Over
Mitosis vs. Meiosis Card Sort
Cell Division Vocabulary Squares

60. Meiosis occurs in germ cells to produce reproductive cells (gametes)
4 haploid daughter cells formed (only one of each chromosome)
Preceded by interphase and DNA replication
Two Divisions:
Meiosis I
Meiosis II

61. The Human Karyotype
Homologous Chromosomes
chromosome pair, one from each parent, that are similar in length, gene position and centromere location

62. Meiosis- click for video clip
Meiosis I- reduction division; like mitosis but only one copy of each homologous chromosome goes to each new cell; two new cells formed
Prophase I
Metaphase I- homologous chromosomes line up on equator to form a tetrad; crossing over occurs
Anaphase I- homologous chromosomes separate
Telophase I- two new cells, each with half the genetic material
Meiosis II- the two cells formed in Meiosis I divide again, with sister chromatids separating
Basically like Mitosis 62

63. Meiosis I - Reduction Division
Interphase I
Prophase I
Metaphase I
Anaphase I
Each chromosome pairs with its corresponding homologous chromosome to form a tetrad.
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Homologous chromosomes line up along the middle of the cell.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward the opposite ends of the cell.

64. Meiosis I - Reduction Division
Interphase I
Prophase I
Metaphase I
Anaphase I
Crossing over- exchange of genes between homologous chromosomes- increases genetic variation among offspring
Cells undergo a round of DNA replication, forming duplicate Chromosomes.
Homologous chromosomes line up along the middle of the cell.
Spindle fibers attach to the chromosomes.
The fibers pull the homologous chromosomes toward the opposite ends of the cell.
This reduces the chromosome number in each daughter cell by half.

65. Meiosis II - Similar to Mitosis
Prophase II
Metaphase II
Meiosis I results in two haploid (N) daughter cells, each with half the number of chromosomes as the original.
The chromosomes line up in a similar way to the metaphase stage of mitosis.
Anaphase II
Telophase II
The sister chromatids separate and move toward opposite ends of the cell.
Meiosis II results in four haploid (N) daughter cells.

66. Modeling Crossing Over
Use the paper to create a model of crossing over
First, draw a pair of duplicated homologous chromosomes using two different colors.
Model how the homologous chromosomes separate during Meiosis I
Model how the sister chromatids separate during Meiosis II

67. Mitosis vs. Meiosis Animation Mitosis- 2 diploid cells produced
Meiosis- 4 haploid cells produced
Why? 67

68. Comparing Mitosis and Meiosis
Place the cards in order
How are the two processes similar? How are they different?

69. Meiosis Using two successive divisions to reduce the number of chromosomes by half and create gametes.
Homologous chromosomes: a pair of chromosomes with the same genes (but may have different alleles); one from each parent.

70. Mitosis vs. Meiosis Mitosis Meiosis 1 2 4 46 (diploid) 23 (haploid)
# of divisions 1 2
# of daughter cells produced 4
# chromosomes in parent cell
46 (diploid)
# chromosomes in daughter cell
23 (haploid)
Type of cells produced
Somatic (body) cells
Gametes (sex cells) +*