Ch 12: Cell Cycle
From Topic 1.1(in PowerPoint lecture)
Understandings:
• Specialized tissues can develop by cell differentiation in multicellular organisms.
• Differentiation involves the expression of some genes and not others in a cell’s genome.
• The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.
Applications and skills:
• Application: Use of stem cells to treat Stargardt’s disease and one other named condition.
• Application: Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues.
International-mindedness:
• Stem cell research has depended on the work of teams of scientists in many countries who share results thereby speeding up the rate of progress. However, national governments are influenced by local, cultural and religious traditions that impact on the work of scientists and the use of stem cells in therapy.
Utilization:
• The use of stem cells in the treatment of disease is mostly at the experimental stage, with the exception of bone marrow stem cells. Scientists, however, anticipate the use of stem cell therapies as a standard method of treating a whole range of diseases in the near future, including heart disease and diabetes.
Aim 8: There are ethical issues involved in stem cell research, whether humans or other animals are used. Use of embryonic stem cells
involves the death of early-stage embryos, but if therapeutic cloning is successfully developed the suffering of patients with a wide variety of conditions could be reduced.
Chapter 12: Cell Cycle
From Topic 1.6
Essential idea: Cell division is essential but must be controlled.
Nature of science: Serendipity and scientific discoveries—the discovery of cyclins was accidental (1.4).
Understandings:
• Mitosis is division of the nucleus into two genetically identical daughter nuclei.
• Chromosomes condense by supercoiling during mitosis.
• Cytokinesis occurs after mitosis and is different in plant and animal cells.
• Interphase is a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
• Cyclins are involved in the control of the cell cycle.
• Mutagens, oncogenes and metastasis are involved in the development of primary and secondary tumours.
Applications and skills:
• Application: The correlation between smoking and incidence of cancers.
• Skill: Identification of phases of mitosis in cells viewed with a microscope or in a micrograph.
• Skill: Determination of a mitotic index from a micrograph.
Guidance:
• The sequence of events in the four phases of mitosis should be known.
• Preparation of temporary mounts of root squashes is recommended but phases in mitosis can also be viewed using permanent slides. • To avoid confusion in terminology, teachers are encouraged to refer to the two parts of a chromosome as sister chromatids, while they are attached to each other by a centromere in the early stages of mitosis. From anaphase onwards, when sister chromatids have separated to form individual structures, they should be referred to as
From Topic 1.6
International-mindedness:
• Biologists in laboratories throughout the world are researching into the causes and treatment of cancer.
Utilization:
• The mitotic index is an important prognostic tool for predicting the response of cancer cells to chemotherapy.
Aim 8: The tobacco industry could be discussed. Suppression of the results of research by tobacco companies into the health effects of smoking tobacco was unethical. Smoking causes considerable social harm, but, with the exception of laws on production and supply in Bhutan, has never been made illegal.
From Topic 3.1 Understandings:
• The genome is the whole of the genetic information of an organism.
From Topic 3.4 Understandings:
• Radiation and mutagenic chemicals increase the mutation rate and can cause genetic diseases and cancer.
Applications and skills:
• Application: Consequences of radiation after nuclear bombing of Hiroshima and accident at Chernobyl.
From Topic 6.4
Applications and skills:
• Application: Causes and consequences of lung cancer.
Aim 8: The social consequences of lung cancer and emphysema could be discussed.
Key Roles of Cell Division
•
Reproduction, Growth
&Development, and
Repair
•
Reproduction
- Unicellular divide from one to
two to reproduce entire
organism (fission, budding)
- Multicellular organisms grow
and develop or replace
damaged or dead cells.
•
Cell division results in
identical hereditary
Cellular Division
•
Replicates the DNA
exactly.
•
Allocates two
copies of DNA to
opposite ends of
the cell.
Heredity
•
Total hereditary material of a
species is called its
genome
.
•
Offspring acquire genes from
parents by inheriting
chromosomes.
•
DNA-
Nucleic acid that codes for the
formation of proteins. Made of four
different nucleotides.
•
Genes-
The length of DNA that
codes for a protein.
Chromosome Condensation
http://www.dnalc.org/view/15482-DNA-packaging-3D-animation-with-advanced-narration-and-labels.html
•
DNA coils around 8 Histone Proteins
and then keeps coiling to condense to
be a chromosome
Kinetochores
Cell Cycle Overview
Phases of the Cell Cycle
•
Interphase
: when cell grows,
copies its chromosomes, and
prepare for cell division
•
90% of cell cycle
•
lots of activity
•
Metabolism, Protein synthesis,
DNA Replication and increase in
number of mitochondria and
chloroplasts.
•
Three phases
•
G
1: First growth phase (G = gap)
•
S
: Synthesis
Cell Division: Mitotic (M) Phase
•
M Phase contain two parts:
•
Mitosis:
division of nucleus
•
Cytokinesis
: division of the
cytoplasm
Mitosis
•
Very reliable (one error in 100,000 divisions)
•
Mitosis:
has four stages (PMAT)
•
Prophase
•
Metaphase
•
Anaphase
Mitosis: Prophase
•
Prophase
•
Nucleoli disappear
•
Chromatin condense
•
Spindle forms and attaches to Chromosomes
Mitosis: Metaphase
•
Metaphase
•
The centrosomes are at opposite ends
•
Chromosomes are at metaphase plate
•
Centromeres are all lined up
•
Spindle fully formed.
•
How was this possible?
Mitosis: Anaphase
•
Sister chromatids split
•
Kinetochore fibers shorten
•
Nonkinetochore fibers
How Sister Chromatids Gets Separated?
Mitosis: Telophase
•
Nonkinetochore further elongate
•
Daughter nuclei begin to form
•
By the end, the two nuclei are clearly visible in their
interphase appearance.
Cytokinesis
•
In animal cells, pinching forms a
cleavage furrow
.
•
Contractile ring of actin fibers pinch the cells in two.
•
In plant cells, the golgi apparatus secretes vesicles that fuse in the middle to
form the
cell plate
. More will be added until a new middle lamella forms and
new cellulose is laid down on either side.
Cell Cycle Control System
•
Check points or switches control the rate of the cell cycle
•
Can either be intracellular and extracellular control
•
G1 checkpoint or the Restriction point is said to be the
beginning of the cell cycle.
Cell Cycle Regulation: Intracellular
•
Protein
kinases
are enzymes that transfer a phosphate group from
ATP to a target protein
•
They can either activate or inactivate
•
Some kinases give the “go-ahead” signal to bypass the G
1
and G
2
checkpoints.
•
They are present at constant concentration, but are usually in
inactive “dormant” form.
•
These kinases are regulated by
cyclins,
a protein that cyclically
fluctuates in concentration inside the cell.
Cdk: MPF
•
MPF:
a type of Cdk that was first discovered in the cell; short for
“maturation-promoting factor” or “M-phase-“maturation-promoting factor” since it triggers the cell to pass
G
2checkpoint into M phase
•
Acts directly as a kinase as well as activating other kinases
Cdk: MPF Review
• http://www.sinauer.com/cooper5e/animation1604.html
•
http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/007 2437316/120082/bio34a.swf::Control%20of%20the%20Cell%20Cycle
• http://www.cleanvideosearch.com/media/action/yt/watch?v=QGx50C 1w8YY
Cell Cycle Regulation: External Factors
•
Chemical Factors
•
All kinetochores need to be attached to chromosomes in
order for anaphase to begin.
•
Growth factors
•
Physical factors
•
Density Dependent Inhibition:
when cells get crowded,
they stop dividing.
•
Anchorage dependence
: cells must be attached to
Differentiation
•
Differentiation:
or “differential gene expression” (from Ch 19.2 of your
Campbell textbook); expression of different genes by cells with the same
genome
•
Stem Cells:
an undifferentiated cell that is capable of giving rise to indefinitely
more cells of the same type, and from which certain other kinds of cell arise
by differentiation
•
Totipotent
•
can produce any cell from placenta to embryo
•
Pluripotent
•
can produce any cell from embryo…
etc, but not placenta
•
Multipotent
•
“Adult stem cells” ….
like in bone marrow
Stem Cell Research
•
The Promise of Stem Cell Research: Ted Talk
https://www.ted.com/talks/susan_solomon_the_promise_of_research_with_stem_cells
•
Stem Cell Stories:
http://www.eurostemcell.org/films#ipsfilm•
Stargardt’s Disease:
http://www.youtube.com/watch?v=vvrlpVPxYiE•
Stargardt’s Disease and Stem Cell Research:
Intro to Cancer
•
Tumor
is a mass of cells
that have lost their ability
to stop dividing.
•
Malignant Tumors:
•
Can impair normal function of
tissue, organ
•
Altered cell cycle, excessive
divisions
•
May have different # of
chromosomes
•
Altered metabolism
•
Doesn’t not show DDI
•
Benign Tumors:
•
Stay at the original site
Cancer Cells
•
No response to DDI
•
May make excess growth factors
•
May have different signaling systems
•
Normal checkpoints are not working
Metastasis
•
Metastasis-
cells move from original location
•
move in blood, lymph vessels
Lung Cancer
Causes:
•
Smoking
•
Passive Smoking
•
Asbestos Fibers
•
Radon Gas
•
Family history
•
Lung Disease
•
Air pollution (1-2% of lung cancer
deaths attributed to this)
Consequences:
•
Chronic, hacking, raspy coughing,
sometimes with blood-streaked mucus
•
Recurring respiratory infections,
including bronchitis or pneumonia
•
Increasing shortness of breath,
wheezing, persistent chest pain
•
Hoarseness
•
Swelling of the neck and face
•
Pain and weakness in the shoulder,
arm, or hand
•
Fatigue, weakness, weight loss, and
appetite, intermittent fever, sever
headaches, and body pain
Radiation Risks
Day after Explosion Most Severe Moderately Severe Mild 1. 1. Nausea and vomiting 1. Nausea and vomiting
2. after 1-2 hours. after 1-2 hours. 3. NO DEFINITE SYMPTOMS
4.
5. 2. Diarrhea
6. 3. Vomiting NO DEFINITE SYMPTOMS
7. 4. Inflammation of the mouth and throat
8. 5. Fever
9. 6. Rapid emaciation
10. Death NO DEFINITE SYMPTOMS
11. (Mortality probably100%) 2. Beginning epilation.
12. 13. 14. 15. 16. 17.
18. 3. Loss of appetite
19. and general malaise. 1. Epilation
20. 4. Fever. 2. Loss of appetite
21. 5. Severe inflammation and malaise.
22. of the mouth and throat 3. Sore throat.
23. 4. Pallor.
24. 5. Petechiae
25. 6. Diarrhea
26. 7. Moderate emaciation.
27. 6. Pallor.
28. 7. Petechiae, diarrhea
29. and nose bleeds (Recovery unless
com-30. plicated by previous
31. 8. Rapid emaciation poor health or Death super-imposed in-(Mortality probably 50%) juries or infections).
