1. Cells divide at different rates.
5.1 Cell Cycle
Cells divide at different rates.

2. 5.3 Regulation of the Cell Cycle
KEY CONCEPT Cell cycle regulation is necessary for healthy growth.

3. 5.3 Regulation of the Cell Cycle
External factors include physical and chemical signals.
Growth factors are proteins that stimulate cell division.

4. 5.1 Cell Cycle Cell size is limited.
If volume increases faster than surface area then cell divides
Surface area to Volume Ratio

5. 5.3 Regulation of the Cell Cycle
Apoptosis is programmed cell death.
a normal feature of healthy organisms
occurs in development of infants
webbed fingers

6. KEY CONCEPT Many organisms reproduce by cell division.

7. Asexual reproduction is the creation of offspring from a single parent.
Binary fission produces two daughter cells genetically identical to the parent cell.
occurs in prokaryotes
No nucleus
Ex: bacteria
parent cell
DNA
duplicates
cell begins
to divide
daughter
cells

8. Budding forms a new organism from a small projection growing on the surface of the parent.
Hydra
Yeast

9. Vegetative Reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

10. The Cell Cycle has Three main stages.

11. 5.1 Cell Cycle
Interphase
Gap 1 (G1) – cell growth and normal functions
Synthesis (S): copies DNA
Gap 2 (G2): additional growth
Mitosis (M)
Division of the cell nucleus
Cytokinesis
Division of the cell cytoplasm
Some cells (G0) – exit the cell cycle
fully developed cells in the CNS

12. 5.2 Mitosis and Cytokinesis
Mitosis divides the cell’s nucleus in four phases.
Prophase
chromosomes condense and spindle fibers form
Nucleolus and the nuclear membrane break down & disappear
Centrioles (centrosomes) appear

14. 5.2 Mitosis and Cytokinesis
Metaphase
Chromosomes line up in the middle of the cell.
Chromosomes are easier to identify
Photomicrograph for Karyotype

15. 5.2 Mitosis and Cytokinesis
Anaphase
sister chromatids separate to opposite sides of the cell.

17. 5.2 Mitosis and Cytokinesis
Telophase
New nucleus and nucleolus form
Chromosomes begin to uncoil
Spindle fibers and centrioles disappear

19. 5.2 Mitosis and Cytokinesis
Cytokinesis differs in animal and plant cells.
Cleavage furrow -
(animal cells) the cell membrane pinches in
Cell plate -
(plant cells) a cell wall forms between the two cells

20. 5.2 Mitosis and Cytokinesis
Results of Mitosis
2 new cells genetically identical to the parent cell
2 identical diploid cells.
Single celled eukaryote – asexual reproduction
Multi-celled eukaryote – growth

21. 6.2 Process of Meiosis
KEY CONCEPT During Meiosis, diploid cells undergo two cell divisions that result in 4 different haploid cells.

22. 6.1 Chromosomes and Meiosis
Occurs in sex organs (ovaries & testes)
Produces genetically different sex cells - gametes.

23. 6.2 Process of Meiosis DNA coils tightly into chromosomes
Stages of Meiosis
Interphase – G1, S, G2
Meiosis I
Prophase I
DNA coils tightly into chromosomes
Spindle fibers & centrioles appear
Nucleus & nucleolus disappear
Synapsis - Every chromosome lines up next to its homologue
each pair is called a tetrad – 4 chromatids XX
during synapsis the chromatids may twist around each other which may result in…
crossing over - portions of chromatids break off & attach to the other chromatids
* genetic recombination - the exchange of genetic material between maternal & paternal chromosomes (homologous pair)

24. 6.6 Meiosis and Genetic Variation

25. 6.6 Meiosis and Genetic Variation
Metaphase I
Tetrads line up randomly along the middle of the cell

26. 6.6 Meiosis and Genetic Variation
Anaphase I
Tetrads separate
Each homologous chromosome moves to an opposite pole
Independent Assortment – random separation of the homologous = genetic recombination

27. 6.6 Meiosis and Genetic Variation
Telophase I
Chromosome reach the opposite pole
Cytokinesis begins
Each new cells now contains a haploid # of chromosomes (half the original #)

28. 6.2 Process of Meiosis
DNA is not replicated between meiosis I and meiosis II (No Interphase)

29. 6.2 Process of Meiosis Meiosis II Prophase II
Spindle fibers and centrioles form
Metaphase II
Chromosomes move to the middle of the cells
Anaphase II
Chromatids separate & move toward opposite poles
Telophase II
Nuclear membrane forms around the chromosomes
Cytokinesis II – results in 4 new cells each with half the # of chromosomes each genetically different

30. 6.2 Process of Meiosis
Meiosis has two cell divisions - mitosis has one
Meiosis results in 4 different haploid cells - mitosis results in 2 identical diploid cells

31. After Meiosis Haploid cells develop into mature gametes.
6.2 Process of Meiosis
After Meiosis Haploid cells develop into mature gametes.
Gametogenesis - the production of gametes.
differs between females and males.

32. Spermatogenesis – production of sperm cells
6.2 Process of Meiosis
Spermatogenesis – production of sperm cells
Meiosis = 4 haploid cells – spermatids
Each spermatid then develops into a mature sperm cell
Sperm cells (plural) – spermatozoa

33. Oogenesis – production of mature egg cells – ova (plural)
6.2 Process of Meiosis
Oogenesis – production of mature egg cells – ova (plural)
Meiosis = 1 mature egg cell (ovum)
During cytokinesis the cytoplasm is divided unequally
One cell receives most of the cytoplasm  develops into ovum
Other 3 cells = polar bodies = degenerate (break down)