1. CELL REPRODUCTION
THE CELL CYCLE AND MITOSIS

2. Lesson Objectives—Cell Cycle
Describe the properties of cell division in prokaryotes.
Describe cell division in eukaryotes. Explain the main differences between cell division in prokaryotic and eukaryotic cells.
Describe the basic properties of chromosomes.
Describe the key steps in the cell cycle.
Identify and describe the main processes in mitosis.
Describe how the cell cycle is controlled and define cancer.

3. CELL REPRODUCTION
Cell Division: process by which a cell divides to form two new cells (daughter cells)
Three types of cell division, or cell reproduction
Prokaryotes (bacteria)
Binary fission divides forming two new identical cells
Eukaryotes
Mitosis
Cell or organism growth
Replacement or repair of damaged cells
Meiosis
formation of sex cells, or gametes

4. Why do cells divide? 1: DNA Overload 2: Exchange of materials
If cells grow without limit, an “information crisis” would develop
DNA cannot serve the needs of the increasing size of cell
2: Exchange of materials
Food and oxygen have to cross membrane very quickly
Waste must get out
If cell is too large, this occurs too slowly and cell will die

5. PROKARYOTIC CELL DIVISION
Binary fission
3 main steps:
1: DNA Replication—DNA is copied, resulting in 2
identical chromosomes
2: Chromosome Segregation—2 chromosomes separate,
move towards ends (poles) of cell
3: Cytokinesis—cytoplasm divides, forming 2 cells
Each new daughter cell is
genetically identical to parent cell

6. THE CELL CYCLE
G1 phase
M phase
S phase
G2 phase

7. CELL CYCLE-INTERPHASE
Interphase: period of growth and DNA replication between cell divisions
Three phases:
G1 Phase
cell increases in size
S Phase
Replication of chromosomes
Now two strands called sister chromatids joined by a centromere
G2 Phase
organelles double
new cytoplasm forms
All other structures needed for mitosis form

8. DNA containing cell’s genetic code
Each chromosome has a matching pair
-- Homologous Pair
During interphase, each chromosome copies itself

9. EUKARYOTIC CELL DIVISION
DNA found on chromosomes located in nucleus of cell
Cell cycle continuous process
Cells grow
DNA replicated
Organelles duplicated
Divide to form daughter cells
2 Main steps:
1: Mitosis (4 steps—Prophase, Metaphase, Anaphase, Telophase)
Nucleus divides
2: Cytokinesis—Cytoplasm divide, forming 2 cells
Each new daughter cell is genetically identical to parent cell

10. Mitosis = nuclear division
Mitosis is followed by cytokinesis (cell division)
The steps of mitosis ensure that each new cell has the exact same number of chromosomes as the original

11. MITOSIS
Process that divides cell nucleus to produce two new nuclei each with a complete set of chromosomes
Continuous process
Four phases (PMAT)
Prophase
Metaphase
Anaphase
Telophase

12. PMAT (1)Prophase (2)Metaphase (3)Anaphase (4)Telophase Interphase 1 2
Cytokinesis

13. 1. chromosomes visible (sister chromatids)
2. centrioles migrate to the poles (only in animals)
3. nuclear membrane disappears
4. spindle forms

14. chromosomes line up on the equator of the cell
spindles attach to centromeres
Equator

15. sister chromatids separate
centromeres divide
sister chromatids move to opposite poles

16. 1. chromosomes uncoil • now chromatin
2. nuclear membranes reform
3. spindle disappears

17. Occurs at end of Mitosis
--division of the cytoplasm to form 2 new daughter cells
--organelles are divided
-Daughter cells are genetically identical
Cells return to interphase

19. Name the phases starting at the top.
Mitosis
Name the phases starting at the top.

20. 2.Name the phase
3.Identify X
4.Identify Y

21. 5. Name the phase

22. 6. Name the phase

23. Control of the Cell Cycle
Regulatory proteins called cyclins control the cell cycle at checkpoints:
G1 Checkpoint—decides whether or not cell will divide
S Checkpoint—determines if DNA has been properly replicated
Mitotic Spindle Checkpoint—ensures chromosomes are aligned at mitotic plate

24. Cell Cycle Checkpoints

25. CANCER CELLS
Result of uncontrolled cell division of cells that have lost ability to regulate cell cycle
Reproduce more rapidly than normal cells
Masses formed called ‘tumors’
Can be caused by:
Cell’s DNA is damaged
Radiation
Toxic chemicals
May form a tumor (mass of abnormal cells)

26. Lesson Summary—Cell Cycle
The cell cycle is a repeating series of events, characterizing the life of a eukaryotic cell.
Binary fission is a form of cell division in prokaryotic organisms that produces identical
offspring.
As a eukaryotic cell prepares to divide, the DNA and associated proteins coil into a
structure, known as a chromosome.
The DNA copies during the S phase of the cell cycle, resulting in a chromosome that
consists of two identical chromatids, known as sister chromatids, attached at a region
called the centromere.
Any cell containing two sets of chromosomes is said to be diploid; the zygote forms
from the fusion of two haploid gametes.
The cell cycle has five phases: the first growth (G1) phase, the synthesis (S) phase,
the second growth (G2) phase, mitosis, and cytokinesis.
Mitosis is the division of the nucleus; four distinct phases of mitosis have been
recognized: prophase, metaphase, anaphase, and telophase.
Cytokinesis is the division of the cytoplasm.
The cell cycle is controlled through feedback mechanisms.
Cancer results from uncontrolled cell division, due to the loss of regulation of the cell
cycle.