1. Limits to Cell Growth
? Do cells grow larger to increase the size of the organism?
NO!!
Why?
1) DNA
- cell parts rely on DNA for instructions
- increase in size = more parts needing info
* DNA has a limit on ability to send out
instructions

2. 2) Movement of Materials
- increase in size = larger volume (inner space)
less surface area (cell membrane)
Therefore:
- materials get crowded moving in/out of cell
Example: 1cm x 1cm cell 3cm x 3cm cell
Surface Area = 1cm x 1cm x 6 sides 3cm x 3cm x 6
= 6 cm2 = 54 cm2
Volume = 1cm x 1cm x 1cm 3cm x 3cm x 3cm
= 1cm3 = 27 cm3
Ratio = 6 to to 1

3. - Cell division increases the number of cells
Solution
- Cell division increases the number of cells
which increases the organism’s size.

4. Biology is the only subject in which multiplication is the same thing as division…

5. MITOSIS: Making New Cells Making New DNA

6. Where it all began…
We all start as a cell smaller than a period at the end of a sentence…

7. And now look what can happen…
How did you get from there to here?

8. Getting from there to here…
Going from egg to baby….
the original fertilized egg has to divide…
and divide…

9. Why do cells divide… One-celled organisms Multi-celled organisms
for reproduction
asexual reproduction (clones)
Multi-celled organisms
for growth & development
from fertilized egg to adult
for repair & replacement
replace cells that die from normal wear & tear or from injury
amoeba
starfish
Unicellular organisms
Cell division = reproduction
Reproduces entire organism& increase population
Multicellular organisms
Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg
Also use cell division to repair & renew cells that die from normal wear & tear or accidents

10. Dividing cells… What has to be copied DNA organelles cell membrane
lots of other molecules
enzymes
plant cell
animal cell

11. Copying DNA A dividing cell duplicates its DNA
creates 2 copies of all DNA
separates the 2 copies to opposite ends of the cell
splits into 2 daughter cells
But the DNA starts loosely wound in the nucleus
If you tried to divide it like that, it could tangle & break
DNA
cell
nucleus

12. Copying & packaging DNA
When cell is ready to divide…
copy DNA first, then…
chromosomes COIL UP like thread on a spool…
now can move DNA around cell without having it tangle & break
Copying DNA
Coil DNA into compact chromosomes

13. Organizing & packaging DNA
cell
nucleus
DNA has been “wound up”
DNA in chromosomes in everyday “working” cell
cell
nucleus
4 chromosomes in this organism
DNA in chromosomes in cell getting ready to divide

14. DNA must be duplicated…
chromosomes in cell
4 single-stranded chromosomes
nucleus
cell
DNA in chromosomes
nucleus
cell
duplicated chromosomes
duplicated
chromosomes
4 double-stranded chromosomes

15. double-stranded human chromosomes
ready for mitosis

16. Chromosomes of Human Female
23 pairs

17. Chromosomes of Human Male
23 pairs

18. Cell Cycle: Life Cycle of Cells
Stage 1: cell copies DNA
- period of growth & division of a cell
DNA
Interphase
3 Stages
G1 phase- cell growth
S phase- DNA replication
G2 phase- new organelles
cell
nucleus

19. Cell Cycle

20. Mitosis: Dividing DNA & cells
Stage 2: DNA winds up into chromosomes
DNA is wound up into chromosomes to keep it organized
duplicated chromosomes
(prophase)
cell
nucleus

21. Mitosis: Dividing DNA & cells
Stage 3: Chromosomes line up
chromosomes line up in middle
attached to protein “cables” that will help them move
metaphase
duplicated chromosomes
lined up in middle of cell

22. Mitosis: Dividing DNA & cells
Stage 4: Chromosomes separate
chromosomes split, separating pairs
start moving to opposite ends
anaphase
chromosomes split & move to opposite ends

23. Mitosis: Dividing DNA & cells
Stage 5: Cell starts to divide
cells start to divide
nucleus forms again
Telophase
- Animals - cell pinches in
- Plants- cell plate forms

24. Mitosis: Dividing DNA & cells
Stage 6: DNA unwinds again
cells separate
now they can do their every day jobs
cytokinesis

25. New “daughter” cells Get 2 exact copies of original cells same DNA
“clones”

26. Cell division in Animals

27. Mitosis in whitefish embryo

28. Mitosis in plant cell

29. onion root tip

30. Please Make Another Two Cells
I.P.M.A.T.C.
Overview of mitosis
interphase
prophase
Please Make Another Two Cells
cytokinesis
metaphase
anaphase
telophase

31. Any Questions??