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

2. The Cell Cycle: Cell Growth, Cell Division, Mitosis & Meiosis

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

4. Getting from there to here…
Cell division
continuity of life = reproduction of cells
reproduction
unicellular organisms
growth
repair & renew
Cell cycle
life of a cell from origin to division into 2 new daughter cells
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

5. Getting the right stuff
What is passed to daughter cells?
exact copy of genetic material = DNA
this division step = mitosis
assortment of organelles & cytoplasm
this division step = cytokinesis

6. Copying DNA Dividing cell duplicates DNA
separates each copy to opposite ends of cell
splits into 2 daughter cells
human cell duplicates ~3 meters DNA
separates 2 copies so each daughter cell has complete identical copy

7. Cell cycle Cell has a “life 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 G0
epithelial cells, blood cells,
stem cells
brain nerve cells

8. Cell Division cycle Phases of a dividing cell’s life interphase
cell grows
replicates chromosomes
produces new organelles
mitotic phase
cell separates & divides chromosomes
mitosis
cell divides cytoplasm & organelles
cytokinesis

9. Interphase 90% of cell life cycle Characteristics nucleus well-defined
DNA loosely packed in long chromatin fibers

10. Mitosis copying cell’s DNA & dividing it between 2 daughter nuclei
Mitosis is divided into 4 phases
prophase
metaphase
anaphase
telophase

11. Prophase DNA condenses visible as chromosomes
Centrioles move to opposite poles of cell
Spindle forms
Nucleolus disappears
Nuclear membrane breaks down

12. Metaphase Chromosomes align along the middle of cell meta = middle
helps to ensure chromosomes separate properly
so each new nucleus receives only 1 copy of each chromosome

13. Anaphase Sister chromatids separate Poles move farther apart
move to opposite poles
Poles move farther apart

14. Telophase Chromosomes arrive at opposite poles Cytokinesis begins
nuclei form
nucleoli form
chromosomes disperse
Cytokinesis begins
cell division

15. Cytokinesis Animals Cleavage occurs
The cytoplasm is beginning to divide in half
Division of cytoplasm happens quickly.

16. Cytokinesis in Animals

17. Mitosis in whitefish blastula

18. onion root tip

19. Methods of Asexual Reproduction
Binary Fission
Budding
Sporulation
Vegetative Propagation

20. Asexual reproduction Bacteria
Divide by binary fission
equal division of both the cytoplasm and nucleus to form two identical organisms
Single-celled eukaryotes reproduce asexually
yeast
Amoeba
Simple multicellular eukaryotes reproduce asexually
Hydra
budding

21. Sporulation spore formation
is reproduction involving specialized single cells coming from one parent
the diagram of mold spores being formed below is an example of this

22. Vegetative Propagation
Production of a new plant from a portion of another plant, such as a stem or branch.

23. + 46 46 92 How about the rest of us?
What if a complex multicellular organism (like us) wants to reproduce?
joining of egg + sperm
Do we make egg & sperm by mitosis? 46 + 46 92
egg
sperm
zygote

24. How do we make sperm & eggs?
reduce 46 chromosomes  23 chromosomes
half the number of chromosomes 23 46 23 46
egg
meiosis 23 46 23
fertilization
sperm

25. Meiosis = reduction division
special cell division in sexually reproducing organisms
reduce 2n  1n
diploid  haploid
half
makes gametes
sperm, eggs

26. Double division of meiosis
DNA replication
1st division of meiosis separates homologous pairs
2nd division of meiosis separates sister chromatids

27. Mitosis vs. Meiosis Mitosis Meiosis 1 division
daughter cells genetically identical to parent cell
produces 2 cells
2n  2n
produces cells for growth & repair
no crossing over
Meiosis
2 divisions
daughter cells genetically different from parent
produces 4 cells
2n  1n
produces gametes
crossing over

28. Crossing over During Prophase 1
homologous pairs swap pieces of chromosome
sister chromatids intertwine
crossing over
tetrad