1. THE CELL CYCLE
The cell cycle: is a series of events that cells go through as they grow and divide
Intro rap
2:16

2. THE CELL CYCLE
As cells increase in size the ratio of surface area to volume decreases
A cube: 2x2x2 S.A.= 24 & Vol. = 8 or 3:1
A cube: 3x3x3 S.A = 54 & Vol. = 27 or 2:1
As cells increase in size there are increased demands on :
DNA: coding for proteins and regulating the cell
Uses up food and oxygen more quickly
Cellular transfer functions:
uptake of food & nutrients
Removal of waste materials
Cells must divide to maintain maximum efficiency.

3. THE CELL CYCLE cell cycle overview
3:18

4. INTERPHASE Interphase consists of 3 stages.
(G1):The Gap 1 phase is when cells grow and make RNA, proteins, and other macromolecules.
The S or Synthesis phase is when the cell is making DNA.
(G2): The Gap 2 phase is when the cell prepares for cell division and makes proteins and organelles that are involved in cell division
Note: If a cell “decides” not to divide, then it enters a dormant phase called G0, which is a non-dividing phase

5. INTERPHASE ATP is synthesized. Proteins are made.
Organelles are formed.
Chromosomes are copied.
Specialized tasks are performed
Damaged parts are repaired..
Wastes are excreted.

6. DNA Replication During the S phase of the cell cycle, DNA replicates.
A short section of the DNA uncoils.
New nucleotides bond to the open sections of the DNA.
The “new” and “old” sections of DNA separate and now there are 2 DNA strands.

7. M-PHASE
Mitosis is the process by which the nucleus of the cell is divided into two nuclei, each with the same number and kind of chromosomes as the parent cell.
this process occurs in body cells (somatic cells), for the purpose of:
Growth
Replacing damaged or old cells.
This is a complex process requiring different stages

9. MITOSIS Mitosis consists of four phases Prophase Metaphase Anaphase
mitosis overview 3:18
Mitosis consists of four phases
Prophase
Metaphase
Anaphase
Telophase

10. Prophase Longest phase. 50-60% of the time in mitosis
Chromatin coils. (condenses)
Nuclear membrane breaks down
Nucleolus disappears
Centrioles migrate.
Mitotic Spindle forms.
Chromosomes attach to the spindles at the centromere and coil tighter.

11. Metaphase
Microtubules connect to the centromere (kinetochore) of each Chromatid pair
Chromatids line up in the center of the cell

12. Anaphase Centromere splits.
Chromatids are separated. Sister chromatids move to the opposite sides of the cell, toward the centrioles.
Chromatids are now called chromosomes.
Anaphase ends when the chromosomes stop moving

13. Telophase Spindles break apart 2 new Nuclear membranes reform.
Chromosomes uncoil (revert to chromatin form)
Nucleolus becomes visible.
Mitosis is complete; but Cell Division is not

14. Cytokinesis Continuous with telophase Cell elongates Animal cells:
Cleavage furrow forms
Plant Cells:
Cell Plate forms
The cytoplasm divides and two identical daughter cells are formed.
Mitosis: Animation/CAD 1:22

15. Rat – epithelial cells

16. Mitosis – Bone Cells 2) Chromosomes copied 1) Parent cell Cells split
3) Chromosomes line up
4) Copies separating
5) 2 daughter cells

17. Differences in Plants
No Centrioles
Centrosomes: these structures take the place of centrioles, and serve as “anchors” for spindle fibers.
During cytokinesis, a cell plate develops midway between the newly formed nuclei. Then, a cell wall develops between the two new cells

18. Plants – apical meristem

19. Cell Cycle Regulators
When cells come into contact with other cells, they respond by not growing (p 250 fig. 10-7)
Cyclins: regulate the timing of the cell cycle in Eukaryotic cells (p251 fig. 10-8)
Internal regulators: proteins that respond to events inside the cell; they allow the cell to proceed only when certain processes have occurred. (i.e. cyclins)
External regulators: proteins that respond to events outside the cell; they direct cells to speed up or slow down the cell cycle (i.e. Growth Factors, neighboring cell’s marker proteins)

20. Uncontrolled Growth
Cancer: is a disorder in which some of the body’s own cells lose the ability to control growth (Cell Cycle)
Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, they form masses of cells called tumors that can damage the surrounding tissues.
The p53 gene normally halts the cell cycle until all chromosomes have been properly replicated; this gene is defective in many cancer cells.
Cancer Rap
3:16

21. Mitosis & Meiosis Videos
Mitosis Animation: optional 1:22
Mitosis & Meiosis Animation and Description: optional 11:00

22. “POTPOURI” KEY CONCEPTS
Cell Cycle
Cell Division: Mitosis & Cytokinesis
Cyclins
Cancer Cells / Tumor
Centromere
Centriole
Sister Chromatids (prophase & metaphase)
P53 gene
Surface Area / Volume Ratio: decreases with cell growth

23. Animations Lab bench: observing mitosis
Lab bench: quiz
Mitosis: interactive animation