1. The Cell Cycle and Cell Division7
The Cell Cycle and Cell Division
AP Biology
Radjewski
2012

2. Chapter 7 The Cell Cycle and Cell Division
Key Concepts
7.2 Binary Fission and Mitosis
7.3 Cell Reproduction Control

3. Two types of Reproduction
Asexual Reproduction
Sexual Reproduction
Faster
Creates genetically identical cells (clones)
Common in nature
Only 1 parent is involved
Examples: binary fission in prokaryotes and mitosis in eukaryotes
Creates gametes (sex cells – sperm and egg cells)
Product has genetic diversity
2 parents are involved
Examples - meiosis
See Chapter 4

4. Asexual Reproduction on a Large Scale

5. Sexual Reproduction on a big scale

6. Basic Term - Chromosome
Consist of DNA and protein
3 forms
Chromatin – 1 long strand, wrapped around histones
Chromatid – half of a chromosome
Chromosome – full X, 2 sister chromatids held together by a centromere
Contain specialized proteins called kinetochores
Homologous Chromosomes – in pairs, similar in shape, size and information (1 from Mom and 1 from Dad) - TETRAD
VIDEO 7.1 Cell Visualization: From DNA to chromosomes
LINK The inheritance of characteristics such as seed shape is discussed in Chapter 8
See Chapter 4

7. Basic Term - Chromosome
VIDEO 7.1 Cell Visualization: From DNA to chromosomes
LINK The inheritance of characteristics such as seed shape is discussed in Chapter 8
See Chapter 4

8. Figure 7.5 The Phases of the Eukaryotic Cell Cycle (Part 1)

9. Two kinds of Cells
Diploid Cells
Haploid Cells
Chromosomes are in pairs
Abbreviated 2n
Example – Somatic (body) cells, zygote
Humans diploid # = 46
Chromosomes are not in pairs
Abbreviated 1n
Example – Gametes/Sex Cells/Sperm/Egg/Spores
Human haploid # = 23

10. Karyotype of Homo sapiens
Mitotic (doubled) chromosomes taken from a white blood cell at metaphase
23 chromosome pairs, 46 total
Stained with Giemsa stain to reveal differences in the DNA/protein associations.
Banding distinctive to each chromosome
What was the sex of this individual?

11. Four events must occur for cell division:
For any cell to divide
Four events must occur for cell division:
Reproductive signal—to initiate cell division
Replication of DNA
Segregation—distribution of the DNA into the two new cells
Cytokinesis—division of the cytoplasm and separation of the two new cells

12. Separates the DNA and cytoplasm into two cells through binary fission
Concept 7.2 Both Binary Fission and Mitosis Produce Genetically Identical Cells
In prokaryotes, cell division results in reproduction of the entire organism.
The cell:
Grows in size
Replicates its DNA
Separates the DNA and cytoplasm into two cells through binary fission

13. C – Cytokinesis – division of the cytoplasm
Cell Cycle
5 parts
G1 - growth
S – DNA Synthesis
G2 – prepare for mitosis
M – mitosis (PMAT)
C – Cytokinesis – division of the cytoplasm
Interphase
See Chapter 9

14. Nucleolus and Nuclear Membrane is Visible
Interphase
3 parts – G1,S,G2
Nucleolus and Nuclear Membrane is Visible
Longest phase of the cell cycle
Chromatin is visible

15. Figure 7.5 The Phases of the Eukaryotic Cell Cycle (Part 2)

16. Chromatin  chromosomes
Prophase
1st stage of mitosis
Chromatin  chromosomes
Centrosome and spindle fibers are visible and start to organize and move to opposite poles
Pair of centrioles
Nuclear Membrane and Nucleolus disappear

17. Metaphase
2nd stage of mitosis
Chromosomes are lined up at the equator of the cell, connected to the spindle fibers by their centromere

18. Chromosomes  chromatids
Anaphase
3rd phase in mitosis
Chromosomes  chromatids
Spindle fibers pull the chromosomes apart and move them towards opposite poles
ANIMATED TUTORIAL 7.1 Mitosis

19. Animal vs. Plant Last phase of mitosis
Telophase
Animal vs. Plant
Last phase of mitosis
Chromatids  chromatin (less compact)
Nuclear membrane and nucleolus return
Overlaps with Cytokinesis
VIDEO 7.4 Division of bacteria, Salmonella enteritidis

20. Division of the cytoplasm (cleavage furrow vs. cell plate)
Cytokinesis
After Interphase
Division of the cytoplasm (cleavage furrow vs. cell plate)
Each daughter cell contains an exact copy of DNA and are identical in every way
See Concept 4.3

21. Figure 7.6 The Phases of Mitosis (1)

22. Figure 7.6 The Phases of Mitosis (2)

23. Concept 7.3 Cell Reproduction Is Under Precise Control
The reproductive rates of most prokaryotes respond to environmental conditions.
In eukaryotes, cell division is related to the needs of the entire organism.
Cells divide in response to extracellular signals, like growth factors.

24. Concept 7.3 Cell Reproduction Is Under Precise Control
Progression is tightly regulated— the G1-S transition is called R, the restriction point.
Passing this point usually means the cell will proceed with the cell cycle and divide.

25. Concept 7.3 Cell Reproduction Is Under Precise Control
Specific signals trigger the transition from one phase to another.
Transitions also depend on activation of cyclin- dependent kinases (Cdk’s).
A protein kinase is an enzyme that catalyzes phosphorylation from ATP to a protein.
Phosphorylation changes the shape and function of a protein by changing its charges.
See Chapter 5

26. Concept 7.3 Cell Reproduction Is Under Precise Control
Cdk is activated by binding to cyclin (by allosteric regulation); this alters its shape and exposes its active site.
The G1-S cyclin-Cdk complex acts as a protein kinase and triggers transition from G1 to S.
Other cyclin-Cdk’s act at different stages of the cell cycle, called cell cycle checkpoints.
See Chapter 3

27. Figure 7.10 Cyclins Are Transient in the Cell Cycle

28. Concept 7.3 Cell Reproduction Is Under Precise Control
Example of G1-S cyclin-Cdk regulation:
Progress past the restriction point in G1 depends on retinoblastoma protein (RB).
RB normally inhibits the cell cycle, but when phosphorylated by G1-S cyclin-Cdk, RB becomes inactive and no longer blocks the cell cycle.
See Chapters 3 and 5
RB + ATP  RB-P + ADP
Active – blocks cell cycle Inactive – allows cell cycle to go forward