1. The Cell cycle
Chapter 12

2. You must know The structure of a duplicated chromosome.
The events that occur in the cell cycle (G1, S, G2).
The role of cyclins and cyclin-dependent kinases in the regulation of the cell cycle.
Ways in which normal cell cycle is disrupted to cause cancer, or halted in certain specialized cells,
The features of mitosis that result in the production of genetically identical daughter cells including replication, alignment of chromosomes (metaphase), and separation of chromosomes (anaphase).

3. Cell Cycle – life of a cell from when it is first formed from a dividing parent cell until its own division into two cells

4. Somatic cells – all “body” cells except for gametes (eggs and sperm)
Called diploid – contain two full sets of chromosomes (one from each parent) – 46 in humans
Gametes are haploid – contain only one set of chromosomes so that when they combine, the zygote formed will contain 2 complete sets again

5. The Chromosome Long sequence of DNA
During interphase, they are found in
chromatin form (thin, stringy)
When replicated, consist of two sister chromatids attached by a centromere which
is composed of protein kinetochores
on each chromatid
Each of the chromatids have
identical DNA sequences

6. Interphase 90% of the cell cycle
G1 phase – cell grows and carries out normal cell functions (protein synthesis, cellular respiration, etc.)
S phase – DNA replication – every chromosome is copied to form sister chromatids (total chromosome # does not change!!!)
G2 phase – more growth, cell functions, preparation for mitosis

7. Mitosis
Division of genetic material (chromosomes) in preparation for cell division
Note: AP does not require you to know the names of the different phases, only the sequence of events

9. 1. Prophase
Chromatin becomes tightly coiled into distinct chromosomes
This also causes the nucleolus to disappear

10. Mitotic spindle begins to form in cytoplasm
Prophase (continued)
Mitotic spindle begins to form in cytoplasm
Consists of microtubules extending from two centrioles in the centrosomes

11. Prometaphase
The nuclear membrane breaks down, allowing microtubules to attach to chromosomes at centromeres

12. Metaphase
Centrioles have migrated to opposite poles
Microtubules move chromosomes to metaphase plate (equator of the cell) – aligned “single file”

13. Anaphase
Sister chromatids are pulled apart by kinetochore microtubules
Cell elongates as non- kinetochore microtubules push away from each other
Opposite poles end up with complete, equal sets of chromosomes

14. Telophase
Nuclear envelopes reform around sets of chromosomes at each pole
Chromosomes start to de- condense to chromotin
Cytokinesis (division of the cell) begins

16. Cytokinesis
Physical division of the cell into two cells
Animals – cleavage furrow forms and cell pinches in two
Plants – cell plate forms to divide cytoplasm and then cell wall & membrane are built upon it

17. Binary Fission
Prokaryotic version of cell divsion

18. Cell Cycle Regulation
Involves a series of checkpoints in which molecular signals tell the cell whether to pause or continue on in the cell cycle

19. G1 phase checkpoint
Most important – if cell passes this checkpoint, will likely complete cell cycle
Cells that do not pass this checkpoint go to G0 phase – non-dividing
Most adult cells remain in G0 (muscle, nerve cells) but some can respond to signals to move back to G1 (liver cells)

20. Checkpoint mechanisms Cyclin-dependent kinases (Cdks)
Cyclins are proteins – production controlled by genes being on/off
Cdks are activated when they bond to a cyclins
Activation of Cdks allows them to produce MPFs – Mitosis Promoting Factors
Accumulation of enough MPFs signal cell to continue on in the cell cycle
During anaphase, MPFs start to “turn off” by initiating the break down of the cyclins – causes mitosis to end

22. Normal Cell Division Control
Density-dependent inhibition – crowded cells don’t divide
Anchorage dependency – cells must be attached to something, such as ECM of a tissue, to divide

23. Cancer – uncontrolled cell division
Transformation – normal cells become cancerous
Do no exhibit density-dependent or anchorage inhibition
Tumor – mass of abnormal cells that divide uncontrollably
Benign – stays in one place
Malignant – tumor impairs organ function
Metastasis – cells of tumor break off and travel to other parts of body