1. Mitosis
Cell division

2. Agenda
Cell cycle
Mitosis Overview
When things go wrong

3. The Expectations
2.5.1 Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis

4. The Cell Cycle… Cells have a life cycle, called the cell cycle
The cell cycle consists of 3 stages:
Interphase (growth and replication)
Mitosis (Nuclear(DNA) division)
Cytokinesis (cytoplasm division)

5. The Cell Cycle G1 Synthesis of DNA for Duplication of chromosomes
Phase of rapid cell growth S
Growth and preparation for cell division
All cells come from preexisting cells
Interphase:
Cells grow, make structural proteins that repair damaged parts, transport nutrients, eliminate wastes, build proteins in preparation for mitosis
Genetic information is called chromatin- all DNA in the nucleus (the tangled fibrous complex of the DNA and protein within a eukaryotic nucleus)
Each chromosome duplicates itself. Each copy is attached together by a centromere. Forming Sister chromatids. Considered one chromosome.
Most time is spent in interphase, nuclear division only a small portion G2 M

6. Interphase
1. Stage G1: primary growth phase. Increase in proteins and in the number of cell organelles.
2. Stage S: indicates the synthesis of DNA. A.k.a- DNA replication
3. Stage G2: Chromosome condensation, preparation for mitosis.
Longest stage of cell cycle (The part where it does not divide). (G1, S, G2). Human cells contain 46 chromosomes during the G1 stage of interphase. This is doubled to 92 strands (still considered 46 chrom) during the S stage of interphase.

7. Stages of Cell Cycle
Mitosis(M phase) –refers to the process of nuclear division
Cytokinesis (C phase)- occurs after mitosis and is the actual physical division of the cell. Not included in mitosis
Interphase: (G1, S, G2)

8. Why do cells divide?
If cells got too large, they would not be able to carry out their functions to survive
Growth: allow organisms to grow from a single cell to a multi-celled organism
Maintenance: allows new cells to replace worn-out or dead cells
Repair: regenerates damaged tissues

9. Why Divide?
It is because the Surface area of a cell to its cytoplasm volume ratio affects the exchange of materials and wastes through the cell.
If surface area were too small for the cytoplasmic volume then the cell couldn’t possibly remove all its waste and get enough nutrients to all parts of the cell to maintain functionality

10. The Basics: Genetic Material
Chromatin in the cell during interphase is structurally loose

11. DNA
Chromosome: DNA and associated proteins (nucleosomes/histones) that help condense chromosome into a smaller area during mitosis.

12. Chromosomes one chromosome one chromosome (unduplicated) (duplicated)
Chromosome: a long piece of coiled DNA and proteins. The number of chromosome in each organism differs. 46 in humans. Seen only when the cell divides.
Sister chromatids: 2 identical copies of the same chromosome
Centromere
Sister Chromatids

13. Difference between Plant and Animal Cell Division
Uses of Mitosis in Eukaryotic Cells:
a. during growth of the individual.
b. when tissues have been damaged and need to be repaired (as in healing of a cut).
c. to reproduce asexually.

14. The Expectations
2.5.2 State that tumours (cancers) are a result of uncontrolled cell division and that these can occur in any organ or tissue

15. Cancer
Mitosis and cell division are under strict control. Only producing cells when needed for growth and repair
Tumour repressive genes- inhibit cell division
Prot-oncogenes- stimulate growth/division

16. Cancer
Cancer: Disorder in which some of the body's cells lose the ability to control their growth.
Tumour - repeated, uncontrolled cell division to form a mass of cells. This can happen in any organ. Some tumours grow large and spread to other parts of the body (metastasis). The diseases caused by the growth of tumours is known as cancer.
Tumours can be benign (harmless) or malignant (spread)

17. Causes Carcinogens (increase chances of mutation leading to cancer)
Radiation (gamma, UV, x-ray etc.)
Chemicals (textile dyes, paints and inks)
Viruses (hepititis B and C and HPV)

18. Removal Surgical- Radiation- Chemotherapy-
physically excise the tumour cells
Radiation-
using strong ionising or nuclear radiation beam which can be directed to a point and burn the cells
Chemotherapy-
Uses chemicals to destroy all rapidly dividing cells by medication. Can destroy other rapidly dividing cells (hair, stomach/intestinal cells, sperm)

19. Cancer vs. Normal cells Cancer cells Normal Cells
Make exact copies of themselves during mitosis
Do not stop reproducing
Reproduce cells
Behave independently
Work dependently/stick together
Metstacize, no controlled death
Self destruct “apoptosis” when old

20. The Expectations
2.5.3 State that interphase is an active period in the life of a cell when many metabolic reactions occur including protein synthesis, DNA replication and an increase in the number of mitochondria and chloroplasts

21. Interphase Most of the time of a cell’s life Many chemical reactions
Biochemical reactions, DNA transcription and translation and DNA relication
# of mitochondria and chloroplasts increase in G2

22. 2.5.4 Describe the events that occur in the four phases of mitosis
The Expectations
2.5.4 Describe the events that occur in the four phases of mitosis
-PMAT-

23. Prophase
*chromatin condenses into chromosomes that contains 2 sister chromatids attached by a centromere
*the nuclear envelope and nucleolus disintegrate
*Mitotic spindle forms from microtubules
*the pair of sister chromatids attach to the spindle at their centromeres.
*in animal cells, a pair of centrioles move to each end, called the poles
* Centrioles move to poles
* Sister chromatids present
* During late prophase the nuclear envelope breaks down and each chromosome is connected to a spindle fibre by its centromere

24. Metaphase
*Each chromosome becomes completely condensed. The chromosomes line up at the centre of the cell. Line up at the equitorial plate (equator)
*The mitotic spindle (made of tubes) is complete and extend from each pole (centrioles) to the middle of the cell.

25. Anaphase
The sister chromatids separate at the centromere. Each is now called a chromosome. The separated chromosome are pulled to opposite poles by the spindle fibres

26. Telophase Chromosomes have arrived at the poles Spindle disappears
Centrioles replicate (in animals)
Nuclear membrane reappears
Nucleolus beocmes visible
Chromosomes become chromatin

27. Cytokinesis
The cell divides the cytoplasm and organelles into two portions (splitting known as cytokinesis)
The cell membrane cleaves inward and in plant cells a cell plate forms, nuclear membrane reforms and spindle disappears
2 identical daughter cells result

28. Mitosis is an Animal cell
Metaphase
Anaphase
Late Prophase
Chromosomes line up
at the equatorial plate.
The nuclear membrane
completely dissolves.
The centromeres divide and the resulting chromosomes, move to opposite poles of the cell. An identical set (homologues) of chromosomes moves to each pole.
Chromosomes continue to condense.
The centrioles assemble and spindle
fibres attach to the centromeres of
the chromosomes. The nuclear membrane
starts to dissolve.
Early Prophase
The chromosomes condense,
becoming shorter and thicker.
The centrioles move to opposite
poles of the cell and spindle
fibres start to form.
Telophase
Chromosomes lengthen again, the spindle fibres dissolve, and a nuclear membrane forms around the chromosomes. In humans, each new nucleus contains 46 unique chromosomes
DNA replicated and cell prepares for division. In humans, 46 chromosomes are duplicated (46 pairs).
Interphase
Telophase
Interphase

29. Cell Death
Apoptosis: regulated or controlled cell death of cells that are no longer useful. This is also used to control cells that have stopped performing properly
E.g your body must produces cells to fight a viral infection. When the infection is gone the cells are removed by apoptosis

30. Mitosis Summary Two divisions occur during cell division
Nuclear division (mitosis) and cytoplasmic division (cytokinesis)
During interphase genetic material is replicated
2 Identical daughter cells produced
Embryonic growth is a result of repeated mitotic divisions
A zygote is one cell after fertilization. As divisions occur, specialization occurs.

31. Any Questions?