1. How Cells Divide-Mitosis
Chapter 7a
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

2. Cell Division in Prokaryotes
Prokaryotic cell division occurs as binary fission in which the cell divides into two halves.
Genetic information exists as a single, circular double-stranded DNA molecule.
Copying begins at replication origin.
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

3. Discovery of Chromosomes
All eukaryotic cells store genetic information in chromosomes.
Most eukaryotes have between 10 and 50 chromosomes in their body cells.
Human cells have 46 (23 pairs).
Copyright © McGraw-Hill Companies
Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

4. Structure of Chromosomes
Chromosomes are composed of chromatin, a complex of DNA and protein.
Heterochromatin and Euchromatin.
DNA exists as a single, long double-stranded fiber extending chromosome’s entire length.
Forms nucleosome every 200 nucleotides.
DNA coiled around histone proteins.
Karyotype - An individual’s particular array of chromosomes.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

5. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

6. Structure of Chromosomes
Diploid - A cell possessing two copies of each chromosome (Human body cells).
Homologous chromosomes made up of sister chromatids joined at the centromere.
Haploid - A cell possessing a single copy of each chromosome (Human sex cells).
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

7. Phases of the Cell Cycle
Five phases of cell division:
G1 - Primary Growth Phase
S - Genome Replicated
G2 - Secondary Growth Phase
Collectively called Interphase
M - Mitosis
C - Cytokinesis
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

8. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

9. G1 - Cells undergo majority of growth.
Interphase
G1 - Cells undergo majority of growth.
S - Each chromosome replicates to produce sister chromatids.
Attached at centromere.
Contains attachment site (kinetochore).
G2 - Chromosomes condense.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

10. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

11. Nuclear Envelope Breaks.
Mitosis
Prophase
Spindle apparatus assembled. Microtubules connect kinetochores on each pair of sister chromatids to the spindle poles.
Nuclear Envelope Breaks.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

12. Chromosomes align in cell’s center. Metaphase plate.
Mitosis
Metaphase
Chromosomes align in cell’s center.
Metaphase plate.
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

13. Sister chromatids pulled towards poles. Poles move apart.
Mitosis
Anaphase
Sister chromatids pulled towards poles.
Poles move apart.
Centromeres move toward poles.
Microtubules shorten.
Telophase
Spindle disassembles.
Nuclear envelope forms around each set of sister chromatids.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

14. Cleavage of cell into two halves. Animal Cells
Cytokinesis
Cleavage of cell into two halves.
Animal Cells
Constriction belt of actin filaments.
Plant Cells
Cell plate
Fungi and Protists
Mitosis occurs within the nucleus.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

15. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

16. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

17. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

18. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

19. Cell Control Cycle
Eukaryotic cells employ centralized controller to regulate cell division. (Go/no-go switches)
G1 - Cell Growth
G2 - DNA Replication
M - Mitosis
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

20. Raven - Johnson - Biology: 6th Ed
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

21. Molecular Mechanisms of Cell Control
Each growing cell binds minute amounts of positive regulatory signals (growth factors) that stimulate cell division.
If neighboring cells use up too much growth factor, there is not enough left to trigger cell division.
Growth factors trigger intercellular signaling systems.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

22. Cell Proliferation-Signaling Pathway
Copyright © McGraw-Hill Companies Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

23. Cancer and Cell Proliferation
Cancer is essentially a failure of cell division control.
Gene p53 plays a role in G1 checkpoint.
Halts cell division if detects damaged DNA and stimulates activity of repair enzymes.
Appears to be absent in many cancerous cells.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

24. Cancer and Cell Proliferation
Growth factors influence cell cycle.
Proto-oncogenes - Positive approach that stimulates cell growth.
Tumor-suppressor genes - Negative approach that inhibits cell division.
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

25. Practice identifying phases:
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

26. Copyright © McGraw-Hill Companies Permission required for reproduction or display
Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies