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

2. MITOSIS: Making New Cells Making New DNA

3. Where it all began…
We all start as a cell smaller than a period at the end of a sentence… S3

4. And now look what can happen…
How did you get from there to here? S4

5. Getting from there to here…
Going from egg to baby….
the original fertilized egg has to divide…
and divide… S5

6. 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 S6

7. Dividing cells… What has to be copied DNA organelles cell membrane
lots of other molecules
enzymes S7
plant cell
animal cell

8. 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 S8

9. 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 S9

10. 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
S10

11. 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
S11

12. double-stranded human chromosomes ready for mitosis

13. Chromosomes of Human Female
23 pairs
S13

14. Chromosomes of Human Male
23 pairs
S14

15. Mitosis: Dividing DNA & cells
Stage 1: cell copies DNA
DNA
interphase
cell
nucleus
S15

16. 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
S16

17. 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
S17

18. Mitosis: Dividing DNA & cells
Stage 4: Chromosomes separate
chromosomes split, separating pairs
start moving to opposite ends
anaphase
chromosomes split & move to opposite ends
S18

19. Mitosis: Dividing DNA & cells
Stage 5: Cell starts to divide
cells start to divide
nucleus forms again
telophase
S19

20. Mitosis: Dividing DNA & cells
Stage 6: DNA unwinds again
cells separate
now they can do their every day jobs
cytokinesis
S20

21. New “daughter” cells Get 2 exact copies of original cells same DNA
“clones”
S21

22. Cell division in Animals

23. Mitosis in whitefish embryo

24. Mitosis in plant cell
S24

25. onion root tip
S25

26. Please Make Another Two Cells
I.P.M.A.T.C.
Overview of mitosis
interphase
prophase
Please Make Another Two Cells
cytokinesis
S26
metaphase
anaphase
telophase

27. Any Questions??