Download The Cell Cycle- Guided Notes

Ch. 12- The Cell Cycle- Guided Notes
Warm Up Questions
1. Define:
1. Genome
2. Gametes
3. Chromatin
4. Chromosome
5. Centromere
6. Kinetochore
7. Checkpoint
8. Cdk
9. MPF
2. What is the longest part of the cell cycle? Why?
3. If the diploid number is 46, the haploid number is?
4. At the end of mitosis and cytokinesis, how do daughter cells compare with their parent cell when it was in G1?
5. At metaphase, if the haploid number is 3, how many chromatids does this cell have?
6. What is the correct phase of the cell cycle/mitosis for the following:
A. Most cells that no longer divide or rarely divide are in this phase
B. Sister chromatids separate and move apart
C. Mitotic spindle begins to form
D. Cell plate or cleavage furrow form
E. Chromosomes replicate
F. Chromosomes line up on equatorial plate
G. Nuclear membrane forms
H. Chromosomes become visible
7. Describe the difference between plant and animal cell division.
8. Measurements of the DNA amount per nucleus were taken. DNA levels ranged from 3-6 picograms per nucleus, what
stage of the cell cycle are these cells in?
A. One nucleus has 3 pgrms
B. One with 6 pgrms
C. 5 pgrms
9. Describe binary fission.
10. How do we know the cell uses chemical signals?
11. Summarize the cell control system.
12. Compare a cancer cell to a normal cell. What goes wrong?
What you must know:
 The structure of the duplicated chromosome.
 The cell cycle and stages of mitosis.
 The role of kinases and cyclin in the regulation of the cell cycle.
1. The Cell Cycle
 Cell Cycle- life of a cell from its formation until it
divides
 Functions of Cell Division
o Reproduction
o Growth
o Tissue Repair
2. Cell Division
 Process by which cell produces more of their kind
o Prokaryotes- binary fission
o Eukaryotes- mitosis and meiosis
3. Genome- all of a cells genetic info (DNA)
 Prokaryote: single, circular chromosome
 Eukaryote: more than one linear chromosomes
o Eg. Human:46 chromosomes, mouse: 40, fruit fly: 8
4. Structure of a Chromosome
 Chromatin
o Raw material that
gives rise to
chromosomes
o Long and thin during
interphase
o Condenses and
becomes visible under
microscope in mitosis
 Each chromosome must be
duplicated before cell division
o Duplicated
chromosome= 2 sister
chromatids attached
by centromeres
5.
Categories of Cells




Somatic Cells
Body cells
Diploid (2n): 2 of
each type of
chromosome
Divide by mitosis
Humans: 2n=46




Gametes
Sex cells (sperm &
egg)
Haploid (n): 1 of
each chromosome
Divide by meiosis
Humans: n=23
6. Phases of the Cell Cycle
 The mitotic phase alternates with
interphase:
o G1  S  G2  mitosis 
cytokinesis
 Interphase (90% of cell cycle)
o G1 Phase: cell grows and
carries out normal functions
o S Phase: duplicates
chromosomes
o G2 Phase: prepares for cell
division
 M Phase (mitotic)
o Mitosis: nucleus divides
resulting in identical complete
copies of chromosomes
packaged into two new nuclei
o Cytokinesis: cytoplasm divides
resulting in two daughter cells
7. Mitosis
 Division of the NUCLEUS
 Mitosis: (PMAT) Prophase  Metaphase  Anaphase  Telophase
 Continuous process with observable structural features:
o Chromosomes become visible (prophase)
o Alignment at the equator (metaphase)
o Separation of sister chromatids (anaphase)
o Form two daughter cells (telophase & cytokinesis)
8. Phases of Mitosis
 Prophase & Prometaphase
(Prepare)
o Nucleus and Nucleolus
disappear
o Chromosomes appear as
connected sister
chromatids
o Mitotic spindle (made of
microtubles) begins to
form
o Centrosomes (pair
centrioles) move to
opposite ends of cell
(plant cells do not have
centrioles)

Metaphase (Middle)
o Sister chromatids line
up along the middle of the cell
o Ready to split
 Anaphase (Apart)
o Sister chromatids
split move on microtubles to
opposite poles in cell
o Spindle apparatus
pulls sister chromatids to opposite
poles

Telophase (Two new nuclei)
o Nuclei of newly split cells form
o Nucleoli appear
o Chromatin uncoils
o ONE cell, TWO Nuceli
9. Cyokinesis (Cytoplasm splits)
 Cytoplasm of cell divided
o Animal Cells:
cleavage furrow
o Plant Cells: cell plate
forms
10. Results of Mitotic Phase (M)
 Mitosis produces 2
genetically identical
daughter cells
 The two daughter cells
contain the exact same
number of chromosomes as
the original parent cell
 Daughter cells are DIPLOID
11.
The Mitotic Spindle
 The mitotic spindle is an apparatus of microtubules that
controls chromosome movement during mitosis
 Assembly of spindle microtubules begins in the centrosome,
the microtubule organizing center
 The centrosome replicates, forming two centrosomes that
migrate to opposite ends of the cell, as spindle microtubules grow
out from them
 The spindle includes the centrosomes, the spindle
microtubules, and the asters (a radial array of short microtubules)
 Some spindle microtubules attach to the kinetochores of
chromosomes and move the chromosomes to the metaphase plate
 During anaphase
o Chromosomes walked to poles by motor proteins
o Kinetochore microtubules shorten at ends as they
depolymerize
o Nonkinetochore microtubules from opposite poles
overlap and push against each other, elongating the cell
12. Prokaryote (Bacteria & Archaea) Division
 Simple single-celled organism without
nucleus
 Genetic material:
o single circular chromosome of DNA,
anchored to cell membrane
o Duplicated before division
13. Binary Fission
14. The Evolution of Mitosis
 Since prokaryotes evolved before eukaryotes, mitosis probably evolved from binary fission
 Certain protists exhibit types of cell division that seem intermediate between binary fission and mitosis
15. Cell Cycle Control System
 Checkpoint = control point where stop/go
signals regulate the cell cycle
 Major Checkpoints:
o G1 checkpoint (Most important!)
 Controlled by cell size, growth
factors, environment
 “Go”  completes whole cell
cycle
 “Stop”  cell enters nondividing
state (G0 Phase)
 Nerve, muscle cells stay at
G0; liver cells called back
from G0
o G2 checkpoint
 Controlled by
DNA replication
completion, DNA
mutations, cell
size
o M-spindle (Metaphase)
checkpoint
 Check spindle
fiber
(microtubule)
attachment to
chromosomes at
kinetochores
(anchor sites)
16. Internal Regulatory Molecules
 Kinases (cyclin-dependent kinase,
Cdk): protein enzyme controls cell
cycle; active when connected to cyclin
 Cyclins: proteins which attach to
kinases to activate them; levels
fluctuate in the cell cycle
 MPF = maturation-promoting factor
o specific cyclin-Cdk complex
which allows cells to pass G2
and go to M phase
17. External Regulatory Factors
 Growth Factor: proteins released by other cells to stimulate cell division
o Example: For example, platelet-derived growth factor (PDGF) stimulates the division of human
fibroblast cells in culture
 Density-Dependent Inhibition: crowded cells normally stop dividing; cell-surface protein binds to
adjoining cell to inhibit growth
 Anchorage Dependence: cells must be attached to another cell or ECM to divide
18. Cancer Cells
 Cancer: disorder in which cells lose the ability to
control growth by not responding to regulation.
 multistep process of about 5-7 genetic changes
(for a human) for a cell to transform
 loses anchorage dependency and densitydependency regulation
 Cancer Cells:
o Lack differentiation
o Have abnormal nuclei
Normal Cells
Cancer Cells
o Form tumors
o Undergo metastasis
19. Tumors
 Tumors- mass of abnormal cells
o Benign tumor: lump of
cells remain at original
site
o Malignant tumor:
invasive - impairs
functions of 1+ organs
(called cancer)
o Metastasis: cells
separate from tumor
and travel to other parts
of body
20. Cancer Prevention
 Anyone can get cancer but
there are ways to minimize risk:
o Don’t smoke, legal or illegal (includes hookahs, chew,
2nd-hand smoke)
o Use sun protection
o Exercise and keep weight at ideal level
o Eat 5-7 servings of fruit and veggies a day
o Use screening/preventative measuresbreast/testicle/mole checks
o Practice abstinence or use condoms
o Vaccines (eg. HPV)