1. Cell Growth & Reproduction MITOSIS

2. Cell Growth
When a living thing grows it does so by producing more cells INSTEAD of making the cells it has larger
Whether it be elephant, human, jellyfish or earthworm – all the cells are about the same size
There are two reasons why this happens:
DNA Overload
Exchange of Materials

3. DNA Overload
All the information to run a cell is located in the nucleus as a code of DNA
If the cell were to get bigger and bigger there would not be enough “information” to run the whole cell

4. Why are cells so small? Cells are surrounded by their cell membrane.
Through that membrane the cell must transport everything they need (aka food & wastes).
If there isn’t enough membrane space, cells can’t get or get rid of what they need.
So there must be a balance between surface area (room to move stuff in & out)
and volume (stuff)
2 cm
Surface 24 cm2/
volume 8 cm3 = 3
1 cm
Surface 6 cm2/
volume 1cm3= 6

5. Reproduction: Not as simple as it looks.

6. First things first: Why must cells divide?
ALL CELLS COME FROM OLD CELLS!
Can’t get anything new without working with what you already have!
3 Major Reasons Cells Divide:
Growth – you start as one cell
Development – you get bigger, learn & change
Repair – your cells get worn out

7. What does a cell need to survive?
A FULL set of genetic material (DNA or RNA)
Biggest hurdle to cell division is making sure each cell transfers ALL the DNA when it makes new cells
This gets more difficult as there becomes more DNA to transfer

8. = one bit of
genetic information I II
III IV

9. = one bit of
genetic information

10. To Prevent Mistakes: CHROMOSOMES!
Putting all the DNA into neat packages (called chromosomes) helps jump this hurdle
Chromosomes in red

11. Parts of a Chromosome Chromosome = whole thing Sister Chromatid = each
“arm” of chromosome
Centromere = middle,
Connects chromatids
LABEL YOUR CHROMOSOME

12. Chromosome Terms Un-replicated: Replicated:
Whole thing = Homologous Chromosome
Sister Chromatid
(as long as they’re attached)
Arm
Centromere
(where they’re attached
Centromere
Sister Chromatid
Arm

13. A Cell’s Life A cell’s life can be divided into 2 stages:
Interphase (3 Parts) – Non-dividing stages
Gap 1 (G1)
Growth phase #1 – cells get bigger
Most cells are found in this phase – “Normal Cells”
Synthesis (S)
New DNA is synthesized, or made
Gap 2 (G2)
Growth phase #2
Preparations for division are made
Mitosis (4 parts) – Dividing stages
Prophase
Metaphase
Anaphase
Telophase

15. So… What is Mitosis? (My-toe-sis)
It is the division of somatic cells
Somatic = non-reproducing, any cell that’s not a sperm cell or an egg cell
A single cell divides into TWO daughter cells
These two cells are identical; they have they SAME DNA
Basically, like a cell copy machine
For convenience, we break the process down into 4 stages. But, really is a continuous process.

16. Cell Cycle: Interphase
Interesting things happen
Cells preparing to divide
Genetic material doubles
The cell is doing what it normally does
Interphase G1 M G2 S

17. Now on to division… MITOSIS
Prophase
Chromosomes pair up.
Chromosomes: thicken & become visible; chromatids are joined by centromere
Centrioles move to opposite ends of cell
Nucleolus disappears
Nuclear membrane dissolves
DNA: Chromatin condenses
to Chromosomes

18. Now on to division… MITOSIS
Metaphase
Chromosomes meet in the middle
Chromosomes line
up at equator aka the
metaphase plate
Chromosomes
attached to spindle
fibers (from centrioles)
at centromeres
DNA: Homologous Chromosomes
are in pairs of sister chromatids

19. Now on to division… MITOSIS
Anaphase
Chromosomes get pulled apart
Spindle fibers shorten and pull sister chromatids to the opposite ends of the cell
DNA: Sister chromatids separate
into daughter chromosomes

20. Now on to division… MITOSIS
DNA: Chromosomes
de-condense back to
chromatin
Telophase
Now there are two!
Chromosomes de-condense
Spindle fibers disintegrate
Nuclear membrane forms
And the cell (finally) divides aka CYTOKINESIS

21. Now on to division… MITOSIS
Cytokinesis
Cutting of cell membrane
Different in plants and animals
Animals:
Cell membrane simply pinches (on cleavage furrow) until it splits cell
Plants:
Because of Cell Wall, can’t pinch. Instead, cell grows a cell plate in middle of cell until it connects to sides of wall

25. Onion Root Tip

26. Article hosted on Micscape Magazine (Microscopy-UK).
Onion Root Mitosis
Allium root tip
by Joseph C. Rossi
                               
1) Interphase
2) Prophase
3) Metaphase
4) Anaphase
5) Telophase
Interphase Prophase
Return to index of articles by students on the 'Principles and techniques of photomacrography' course, November 2004, Biomedical Photographic Communications (BPC) program at the Rochester Institute of Technology (RIT).
Article hosted on Micscape Magazine (Microscopy-UK).

27. Metaphase Anaphase

28. Telophase Interphase

31. Paste the link above and choose ‘Movie S10’ at the bottom of the page
Paste the link above and choose
‘Movie S10’
at the bottom of the page
Paste the link above and choose ‘Movies of Cells
Movies of Plants & Movies of Animals

32. This is a complicated process… what happens when things go wrong?
There are several factors that try to control the cell cycle:
Before a cell divides the DNA is checked to make sure it was replicated correctly
Chemical signals tell a cell when to start and stop dividing
Cells also communicate to neighboring cells to tell them to stop growing

33. This is a complicated process… what happens when things go wrong?
CANCER

34. Cancer is a disease of the cell cycle
Cancer is a disease of the cell cycle. Some of the body’s cells divide uncontrollably and tumors form.
Tumors in Liver
Tumor in Colon