1. Cell Cycle (Cell Division)

2. The student is expected to: 5A describe the stages of the cell cycle, including deoxyribonucleic acid (DNA) replication and mitosis, and the importance of the cell cycle to the growth of organisms

3. Write these questions and answer them.
Where are chromosomes found?
How many chromosomes or pairs of chromosomes do we have in each of our cells?
How do we make new human organisms?
How many chromosomes do sperm cells have? How about egg cells?
When a sperm fertilizes an egg, how many chromosomes are present? How many cells are present?
How does the fertilized egg become a baby?

4. Why do cells divide? Increased volume  increased demand
Volume  exponential growth
Surface area  doubles
Lack of surface area triggers cell division

5. Developing multicellular Organism.

6. KEY CONCEPT Cells divide during mitosis and cytokinesis.

13. cells divide at different rates.
The rate of cell division varies with the need for those types of cells.
Some cells are unlikely to divide (G0).

14. Rates of Cell Division Rapid Rarely Skin Digestive tract Bone marrow
Replace worn out or broken down cells
Rarely
Muscle
Nerve (slowest)
Stay in G0 phase

15. Cell growth is coordinated with division.
Surface area must allow for adequate exchange of materials.
Cell growth is coordinated with division.
Cells that must be large have unique shapes.

16. Cell Cycle has 3 main functions

17. 1. Growth

18. 2. Replacement and 3. Repair

19. Cell Cycle G1 – Growth 1 S - Synthesis G2 - Growth 2 Prophase
Interphase (preparation for cell division)
G1 – Growth 1
S - Synthesis
G2 - Growth 2
Mitosis (Division of the nucleus)
Prophase
Metaphase
Anaphase
Telophase
Cytokenesis (Division of the cytoplasm)

21. Interphase 75% of cell’s life spent here Includes G1, S, and G2
Centrioles
75% of cell’s life spent here
Includes G1, S, and G2
Nucleolus

22. Interphase G1 – Growth 1 Cell doubles in size
Some organelles (ribosomes & mitochondria) double in number.
Cells that don’t duplicate, stay at this phase Go

23. Interphase S – Synthesis (to make)
DNA Replication
DNA makes a copy of itself so that each “new” cell has a complete set.

26. Interphase G2 – Growth 2 Spindle fiber are assembled.
The rest of the needed organelles are produced.
The cell is now ready to divide!!!

27. Before we go into Mitosis, we are going to talk about the S sub-phase and exactly what happens there!
DNA Replication

28. DNA Replication
So that identical copies of the cell’s genes, can be passed on to each new cell.
DNA Replication occurs during the S sub-phase of Interphase.

29. Chromosome Centromere- hold copies together
When referring to individual sides,
they are called sister chromatids.
Chromosome
Chromosome
Double Copies
Has gone through DNA Replication – so that each cell gets a complete set of 46.
Chromosome
Single Copy
Centromere-
hold copies
together

30. Which of these is ready to go through cell division?

31. Chromosomes condense at the start of mitosis.
DNA wraps around proteins (histones) that condense it.
DNA double helix
DNA and histones
Chromatin
Supercoiled DNA

32. Mitosis – Division of the nucleus (DNA)
Remember: During Interphase the S sub-phase, we made a copy of DNA and in Mitosis we are separating those copies.

33. occurred but chromosomes
Review: Interphase
Chromatin
DNA Replication has
occurred but chromosomes
are uncoiled

34. 1. Nuclear Envelope begins
Mitosis – Prophase
1. Nuclear Envelope begins
to break down
2.Chromosomes
coil up & condense
4.Spindle Fibers
are put together
3.Centrioles migrate
to opposite poles

35. Mitosis – Metaphase 1.Chromosomes line up at the equator 2.Centrioles
at opposite
poles
3. Spindle Fibers
attach to
chromosomes at
the kinetochore

36. Anaphase Centromeres split Chromatids pulled apart
 now called chromosomes

37. Mitosis – Anaphase(cytokenesis begins here)
2.Spindle
Fibers pull
Sister
Chromatids
apart to
opposite
poles
1.Plasma
membrane elongates
3.Sister
Chromatids
are now
chromosomes
of the new
cell forming
Anaphase is Critical to chromosomal distribution

38. 3rd Phase of Cell Cycle Cytokenesis
Cytokenesis begins with Anaphase and continues to finish with Telophase.
Cytokenesis is the division of the cytoplasm ( organelles and cytosol)
It is not an even distribution thus the 2 daughter cells at the end are not completely identical.

39. Mitosis – Telophase 2 5 1 3 4

40. Telophase is the opposite of Prophase
1. Nuclear Envelope is reformed.
2. Chromosomes uncoil forming Chromatin.
3. Only 1 centriole left – the other will be made in Interphase.
4. Spindle Fibers are dissolved.
5. Cleavage Furrow continues to pinch until the cell is divided to form 2 daughter cells with identical DNA.

41. In animal cells, the membrane pinches closed.
Cytokinesis differs in animal and plant cells.
In animal cells, the membrane pinches closed.
In plant cells, a cell plate forms.

43. Controlling Cell Growth
Stop when touching
Can resume when space (injury)
Contact inhibition
Stop when cannot absorb enough nutrients
Uncontrolled growth: cancer