1. Mitotic Cell Division - Exercise 7
Objectives
-Know the stages of the cell cycle.
-Know why mitosis is important.
-Know what types of cells do mitotic division.
-Distinguish differences between an animal and a plant cell during mitotic division.
-Identify the different stages of mitosis under the microscope and in models.
NOTE: YOU DO NOT NEED TO IDENTIFY CELLS IN A POLAR VIEW.

2. Where one chromosomes is double stranded helices replicates so that we now have 2 helices joined by region called center mere or kinetochore and each of these are now called twin chromatid or sister chromatid because one DNA double helix replicated itself.

3. 0.5 µm
Chromosomes
DNA molecules
Chromo-
some arm
Chromosome
duplication
(including DNA
synthesis)
Centromere
Sister
chromatids
Separation of
sister chromatids
Centromere
Sister chromatids

4. MITOSIS is a growth mechanism providing for the production of clone daughter somatic cells and is partially responsible for the processes of embryonic development, growth, and healing. Objective to create two nuclei (cells). Mitosis is to duplicate a set of chromosomes in a parent cell to two daughter nuclei. All cells have identical genome because raise from one fertilize ovule in a process called mitosis. -Duplication of cells (46 chromosomes) -Produces somatic cells

5. AUTOSOMES
Autosomes these are the non sex determining chromosomes. These are your cells that are involved in mitotic division, such as, liver, skin, bone cells.
Humans- have a total of 46 chromosomes. Twenty two pairs of autosomes and one pair of sex chromosomes.
Cell division in eukaryotes typically involves the distribution of duplication sets of chromosomes in a parent cell to two daughter nuclei (Mitosis or karyokinesis) and the division of the cytoplasmic contents of a parent cell into two daughter cells (cytokinesis). Cell division is only one stage (the last (4th) stage – M) of the cell cycle.
Mitosis is when nuclear material divides (Division of nucleus) and cytokinesis is when cytoplasm divides.

6. Interphase
G1: First growth event. The newly formed cell actively produces RNA and protein as it grows – cell growth.
G0: Period of no growth and it occurs prior to S phase, if it is going to happen.
S-phase: Cell stops producing RNA and switches to DNA replication. Chromosomes are duplicated during the S-phase of the cell cycle. Think of S as Synthesis of DNA.
G2: Once the DNA has been duplicated, the cell enters another round of RNA and protein synthesis and growth – more cell growth.
When cells are in G1, S, and G2, they are often said to be in “interphase” – which literally means, between mitotic division.
Finally the cell will divide, and this stage is called M phase. Chromosomes are too thin to see in the interphase stage under the microscope.

7. THE CELL CYCLE
G1 phase- growth phase where cell makes components for DNA synthesis.
S phase-DNA synthesis, chromosomes replicate. DNA replicates (synthesis)
G2 phase-growth phase where cell makes components for DNA synthesis.
G0 phase-non-dividing cells. Neurons stay in this state.
INTERPHASE-time between cell divisions-everything that is not mitosis.
Mitosis (M-phase)- cell divides:
Prophase
Metaphase
Anaphase
Telophase & Cytokinesis
Interphase is usually about 90%, and mitosis is the remaining
10% of the cell cycle.

8. MITOSIS
A single (2n,diploid) cell divides to form two genetically identical (2n,diploid) daughter cells.
4 stages: Prophase, Metaphase, Anaphase, &Telophase (Cytokinesis)

9. Plant cell division Animal Cell Division
It is necessary to obtain tissues that contain cells that are actively dividing. One such tissue is the root tip.
Note: The viewpoint your looking at cells is called a lateral view.
Each cell can be considered to be a single frame of a motion picture. Also know the parts of the cells when dividing.
Onion root tip (Allium cepa). Most of the cells you see will not be in the M stage of the cell cycle. That is, most cells will be in interphase.
Animal Cell Division
Mitosis is animal cells in most readily seen in early embryonic stages. The blastula stage of an embryo is more or less a spherical ball of cells, and cell division occurs in every imaginable plane of the embryo.
Whitefish blastula.

10. NOTE!!!
A professor could ask you what are the different stages of mitosis? In that case, you would write down prophase, metaphase, anaphase, and telophase.
A professor could ask you the different stages of the cell cycle? In that case, you would include interphase (G1, S, G2), and mitosis (P,M,A,T).

11. Question
How can you tell whether you’re looking at a plant cell or an animal cell?

12. THE CELL CYCLE

13. Growth period: production of proteins and cytoplasmic organelles

14. INTERPHASE
The only significant genetic event occurring here is the replication of DNA (all the chromosomes duplicate).
In interphase the chromosomes are not visible. They exist in thread-like strands known as CHROMATIN
Cell is not diving. Very prominent nucleus (no chromosomes) cell makes protein and lots of RNA.

15. Interphase
These cells have obvious nuclear membranes and the nuclear material is still dispersed as chromatin.

16. PROPHASE CELLS -Chromosomes condense and become visible
When mitosis begins, several changes occur in the cell. The chromosomal material (called chromatin) in the nucleus starts to condense, and eventually reaches thickness that makes them visible under the light microscope.
As prophase proceeds, the chromosomes continue to get shorter and thicker, and eventually begin to move toward the equator of the cell, midway between the poles. Prophase is typically the longest phase of mitosis.
interphase
prophase
-Chromosomes condense and become visible
-Nuclear membrane breaks down
-Nucleoli vanish

17. Prophase
Several cells are seen in various stages of prophase. Note the presence/absence of a nuclear membrane and the spindle apparatus, and the chromatin beginning to condense as visible chromosomes.

18. METAPHASE CELL -chromsomes line up on the center line of the cell
Chromosomes are short and thick will reach the center of the cell called the equatorial plane or metaphase plate. The duplicated chromosomes are separated from one another, except at one point called the kinetochore (centromere). When the duplicate chromosomes are in this attached condition, as they have been since they were duplicated, each strand is called a sister chromatid.
At the conclusion of metaphase each centromere, holding two identical sister chromatids, is attached to two spindle fibers, one from each pole.
-chromsomes line up on the center line of the cell
-centromeres duplicate
-spindle fibers attach to centromeres

19. Metaphase
The two cells in the center are in metaphase. In each, notice the chromosomes are aligned at the cell’s equator and the well formed spindle apparatus.

20. ANAPHASE CELL -Sister chromatids move to opposite poles of the cell
Anaphase begins with the separation of sister chromatids of each duplicated chromosome. Each chromatid is moved by motor molecules that ratchet along the spindle fibers toward the polar ends.
The original chromosome and its exact duplicate are pulled to opposite poles of the cell. This happens for each different chromosome that the cell possesses; thus, each pole will eventually obtain exactly the same set of chromosomes that were in the original nucleus. In anaphase the chromatids are separated.
-Sister chromatids move to opposite poles of the cell
-Spindle fibers pull the chromosomes apart by the centromeres

21. Early Anaphase
The spindle apparatus has begun to separate the chromosomes in the upper cell. The cell near the bottom of the field as in metaphase.

22. Late Anaphase
The chromosomes are close to the centrosomes, which means they have moved apart just about as far as they will go.

23. TELOPHASE CELL
Plant cell
Animal cell
The events of telophase are essentially the reverse of the those of prophase. At the end of this, there are two nuclei, each having identical sets of chromosomes.

24. TELOPHASE
Sister chromatids reach the opposite poles and begin returning to the interphase state.
Nuclear membrane and nucleoli reform.
Spindle fibers disperse.
Cytokinesis occurs.
A cell plate (plants) or a cleavage furrow (animals) forms.

25. Cytokinesis : division of cytoplasm
Animal cells : cleavage
Cleavage furrow
Division begin as a shallow groove in the cell surface near the metaphase plate
Contractile ring (on the cytoplasmic side of the furrow)
Composes of actin microfilaments and the protein myosin
Cleavage furrow deepens until the parent cell is pinched in two
Plant cells : cell plate formation
Vesicles from the Golgi collect at the middle of the cell producing a cell plate
Cell wall material carried in the vesicles is deposited on the plate as it grows, until it fuses with the membrane along the perimeter of the cell

26. Late Telophase and Cytokinesis
The cleavage furrow has nearly divided the two cells, so cytokinesis is almost complete. Telophase will continue with the chromosomes dispersing as chromatin and the nuclear envelope reforming.

27. Polar view
The cell in the center doesn’t fit any of the description because it is begin viewed from one end (pole) rather than from above.

28. The cleavage furrow (CF) has begun to form.

29. Cytokinesis in animal and plant cells

30. Cell Division Reproduction Growth Repair
Equal distribution of genetic material to two daughter cells
Growth
Sexually reproducing organisms develop from a single cell (zygote)
Repair
Replace cells that die from normal wear and tear or accidents
A single-celled eukaryote (amoeba) reproduces
Sand dollar embryo after the egg divided to form 2 cells
Dividing bone marrow cells produce new blood cells

32. Interphase

34. Early Prophase

36. Late Prophase

38. Metaphase

40. Early Anaphase

42. Late Anaphase

44. Telophase - Cytokinesis

46. Interphase 2

47. Animal Vs. Plant Cells
-What are some differences between an animal cell and a plant cell?

48. Animal Vs. Plant Cells
-What are some differences between an animal cell and a plant cell? Plants have a cell wall, after telophase plant cells divide by forming a cell plate, and animal cells form a cleavage furrow. Plant cells are rectangular, and animal cells are more circular.

49. Mitosis - Review

50. Page 8 – Lab Book
1. Why are the onion root tip and the whitefish blastula useful tissues for the study of cell division?
2. Distinguish between mitosis and cytokinesis.
3. If a cell has 16 chromosomes when it is in G1, how many chromosomes will there be in each daughter cell following a mitotic cell division?
4. What are the genetic consequences of mitotic cell division for the resulting daughter cells?
6. How do plant and animal cells differ in the execution of cytokinesis? Why don’t plant cells undergo cytokinesis in the same manner as animal cells?

51. Page 8 – Lab Book
1. Why are the onion root tip and the whitefish blastula useful tissues for the study of cell division? These two tissues were actively dividing, so we (classmates) could find cells under going mitosis at different phases.
2. Distinguish between mitosis and cytokinesis. Mitosis is the division of the nucleus (nuclear division) produces 2 identical nuclei. Cytokinesis is the division of the cytoplasm – produces 2 cells.
3. If a cell has 16 chromosomes when it is in G1, how many chromosomes will there be in each daughter cell following a mitotic cell division? 16
4. What are the genetic consequences of mitotic cell division for the resulting daughter cells? Every cell is genetically identical to each other. Produces 2 identical nuclei, each with the same number and types of chromsomes as the parent cell.
6. How do plant and animal cells differ in the execution of cytokinesis? Why don’t plant cells undergo cytokinesis in the same manner as animal cells?

52. Figure 12.8 Cytokinesis in animal and plant cells

53. Page 9 – Lab Book
7. List several important values or attributes that mitotic cell division provides to multicellular life. In other words, in what ways is mitotic cell division useful for life?
8. List the 4 stages of the cell cycle and describe the primary cellular activity in each stage.

54. Cell Division Reproduction Growth Repair
Equal distribution of genetic material to two daughter cells
Growth
Sexually reproducing organisms develop from a single cell (zygote)
Repair
Replace cells that die from normal wear and tear or accidents
A single-celled eukaryote (amoeba) reproduces
Sand dollar embryo after the egg divided to form 2 cells
Dividing bone marrow cells produce new blood cells

55. Questions 1. How many daughter cells are produced by mitosis?
How does the number of chromosomes in each
daughter cell compare with the number of
chromosomes in the original parent cell after mitosis?
3. When are chromosomes replicated?
During cytokinesis plant cells form a _________
while animal cells form a ____________.

56. Questions 1. How many daughter cells are produced by mitosis? 2
How does the number of chromosomes in each
daughter cell compare with the number of chromosomes
in the original parent cell after mitosis? Same number
and type of chromosomes.
3. When are chromosomes replicated? Interphase, specifically S-phase
During cytokinesis plant cells form a cell plate while
animal cells form a cleavage furrow.