1. Cell Cycle and Mitosis
Biology is the only subject in which multiplication is the same thing as division…
AP Biology

2. Where it all began…
You started as a cell smaller than a period at the end of a sentence…

3. Why do cells divide? For reproduction For growth For repair & renewal
asexual reproduction
one-celled organisms
For growth
from fertilized egg to multi-celled organism
For repair & renewal
replace cells that die from normal wear & tear or from injury
amoeba
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

4. Getting the right stuff
What is passed on to daughter cells?
exact copy of genetic material = DNA
mitosis
organelles, cytoplasm, cell membrane, enzymes
cytokinesis
chromosomes (stained orange) in kangaroo rat epithelial cell
notice cytoskeleton fibers

5. Cell Division allows accurate replication, division & distribution of large genome
Total DNA of a cell of a particular species
Prokaryotic genome
Genomes usually small
Eukaryotic genome
Large genomes
organized into chromosomes
AP Biology

6. Cells have a Life Cycle
AP Biology

7. Interphase 90% of cell life cycle cell doing its “everyday job”
produce RNA, synthesize proteins/enzymes
prepares for duplication if triggered

8. Cell cycle cell is formed from a mitotic division cell grows & matures
to divide again
cell grows & matures to never divide again
G1, S, G2, M
liver cells
G1G0
epithelial cells, blood cells,
stem cells
brain / nerve cells
muscle cells

9. Interphase Divided into 3 phases: G0 G1 = 1st Gap (Growth)
cell doing its “everyday job”
cell grows
S = DNA Synthesis
copies chromosomes
G2 = 2nd Gap (Growth)
prepares for division
cell grows (more)
produces organelles, proteins, membranes G0
signal to divide

10. Interphase Nucleus well-defined Prepares for mitosis
green = key features
Interphase
Nucleus well-defined
DNA loosely packed in long chromatin fibers
Prepares for mitosis
replicates chromosome
DNA & proteins
produces proteins & organelles

11. S phase: Copying / Replicating DNA
Synthesis phase of Interphase
dividing cell must replicate DNA
must separate DNA copies correctly to 2 daughter cells

12. Organizing DNA DNA is organized in chromosomes
ACTGGTCAGGCAATGTC
Organizing DNA
DNA
DNA is organized in chromosomes
double helix DNA molecule
wrapped around histone proteins
like thread on spools
DNA-protein complex = chromatin
organized into long thin fiber
condensed further during mitosis
histones
chromatin
double stranded chromosome
duplicated mitotic chromosome

13. Copying DNA & packaging it…
After DNA duplication, chromatin condenses
coiling & folding to make a smaller package
DNA
mitotic chromosome
chromatin

14. Mitosis Division of cell nucleus
Division of cytoplasm happens quickly.

15. Cytokinesis Animals cleavage furrow forms splits cell in two
like tightening a draw string
Division of cytoplasm happens quickly.

16. Mitosis in whitefish blastula

17. Mitosis in animal cells

18. Cytokinesis in Plants Plants cell plate forms
new cell wall laid down between membranes
new cell wall fuses with existing cell wall

19. Cytokinesis in plant cell

20. Mitosis in plant cell

21. onion root tip

22. Origin of replication
chromosome:
double-stranded DNA
replication
of DNA
elongation of cell
cell pinches in two
ring of proteins
Evolution of mitosis
Mitosis in eukaryotes likely evolved from binary fission in bacteria
single circular chromosome
no membrane-bound organelles