Unit 5 Welcome Back Musical Chairs TODAY Notes on Cell Cycle Become medical school students on oncology rotation Homework for next time Watch Bozeman video on cell cycle mitosis and meiosis There may be a quiz ID: 482806
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Slide1
Cell Cycle, Mitosis, Meiosis
Unit 5Slide2
Welcome Back!
Musical Chairs
TODAY:
Notes on Cell Cycle
Become medical school students on oncology
rotation
Homework for next time: Watch Bozeman video on cell cycle, mitosis and meiosis. There *may* be a quiz.Slide3
Unit 5 Plan
AP Biology Essential Knowledge covered:
In
eukaryotes, heritable information is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization
.
Day 1 – Cell Cycle & Case Study
Day 2 – Mitosis & Case Study
Day 3 – Meiosis & Modeling Activity
Day 4 – Modeling continued, Quiz over notes/
Quizlet
(online)Slide4
Why Care about Cell Cycle Control?
Lifetime Risk of Developing Cancer: Approximately
_____
percent of men and women will be diagnosed with all cancer sites at some point during their
lifetime?
In
2012, there were an estimated
__________ people living with all cancer sites in the United States.Slide5
Why Care about Cell Cycle Control?
Lifetime Risk of Developing Cancer: Approximately
39.6
percent of men and women will be diagnosed with all cancer sites at some point during their
lifetime?
In
2012, there were an estimated 13, 780,000
people living with all cancer sites in the United States.Slide6
Why Care about Cell Cycle Control?
Oncologists – Study cancer
and help those affected
Average salary in 2015 ~ $277,000
Time to become an oncologist?
10-13 years
Bachelors, Medical School, Residency
Demand
?
United States will likely face a
48% increase in demand for oncologist services by 2020—in large part because of the expected 81% increase in cancer survivorship and the 48% increase in cancerincidence caused by the aging of the population. Slide7
Day 1 –
Cell Cycle
In eukaryotes,
heritable information
is passed to the next generation via processes that include the cell cycle and mitosis or meiosis plus fertilization
.
So, passing on heritable information begins with the ability for cells to go through the cell cycle.
Why else is the cell cycle important?Slide8
Some Cell Cycle Basics
The cell cycle is divided into Interphase and Mitotic (including mitosis & cytokinesis)
Interphase
consists of three phases: growth, synthesis of DNA, preparation for mitosis
.
Mitosis consists of prophase, metaphase, anaphase and telophase.
Mitosis alternates with interphase in the cell cycle.
Mitotic PhaseSlide9
Cell division results in genetically identical cellsSlide10
How
do cells know when to divide
?
C
ell communication
signals
chemical signals in cytoplasm give cue
signals usually are
proteins
activators
inhibitors
Activation of cell divisionSlide11
Coordination of cell division
A multicellular organism needs to coordinate cell division across different tissues & organs
critical for normal growth,
development & maintenance
Do you think cells all have
the same timing for their
cell cycle?
Discuss with a friend –
think of an example.Slide12
G
2
S
G
1
M
metaphase
prophase
anaphase
telophase
interphase (G
1
, S, G
2
phases)
mitosis (M)
cytokinesis (C)
C
Frequency of cell division varies by cell type
embryo
cell cycle < 20 minute
skin cells
divide frequently throughout life
12-24 hours cycle
liver cells
retain ability to divide, but keep it in reserve
divide once every year or two
mature nerve cells & muscle cells
do not divide at all after maturity
permanently in G
0
Frequency of cell divisionSlide13
Cell Cycle –
Think/Pair/Share
The cell cycle is a complex set of stages that is
highly regulated
with
checkpoints
, which determine the ultimate fate of the cell.
Why would it need to be highly regulated? What might the checkpoints result in?Slide14
Overview of Cell Cycle Control
Two
irreversible points
in cell cycle
replication of genetic material
separation of sister chromatids
Checkpoints
process is assessed & possibly halted
centromere
sister chromatids
single-stranded
chromosomes
double-stranded
chromosomes
There
’
s no
turning back,
now
!
Slide15
Checkpoint control system
Checkpoints
cell cycle controlled by
STOP
&
GO
chemical signals at critical points
signals indicate if key cellular
processes have been
completed correctly
3 major checkpoints:
G
1
, G
2
and MSlide16
Checkpoint control system
3 major checkpoints
:
G
1
can DNA synthesis begin?
G
2
has DNA synthesis been completed correctly?
commitment to mitosis
M
are all chromosomes attached to spindle?
can sister chromatids separate correctly?Slide17
G
1
Checkpoint is
the
most critical!
primary decision point
“
restriction point
”
if cell receives a
“GO-
ahead”signal
, it will
divide
if cell does
not
receive
signal, it exits cycle &
switches to
G
0
phaseSlide18
G
0
phase
G
0
phase
non-dividing, differentiated state
many human cells in G
0
phase
liver cells
in G
0
, but can be “called back” to cell cycle by external cues
nerve & muscle cells
highly specialized
arrested in G
0
& can never divideSlide19
“Go-ahead”
signals
Protein molecules that promote cell growth & division
internal signals
“
promoting factors
”
external signals
“
growth factors
”
Primary mechanism of control
phosphorylation
Use of
kinase
enzymes
Which either activates or inactivates cell signals by adding a phosphateSlide20
Cell cycle
Chemical
signals
Cyclins
(PROTEIN)
regulatory proteins
levels cycle in the
cell
Cdk’s
(ENZYME)
cyclin
-dependent kinases
phosphorylates cellular proteins
activates or inactivates proteins
Cdk-cyclin
complex
Forms
MPF (mitosis promoting factor)
complex
Triggers movement into next phase
activated Cdk
inactivated
CdkSlide21
Cdk / G
1
cyclin
Cdk / G
2
cyclin (MPF)
G
2
S
G
1
C
M
G
2
checkpoint
G
1
checkpoint
Active
Inactive
Active
Inactive
Inactive
Active
mitosis
cytokinesis
MPF
= Mitosis Promoting Factor
Replication completed
DNA integrity
Chromosomes attached at metaphase plate
M checkpoint
Growth factors
Nutritional state of cell
Size of cellSlide22
Cyclin
&
Cyclin
-dependent
kinases (
Cdk’s
)
CDKs &
cyclin
drive cell from
one phase to next in cell cycle
proper regulation of cell cycle is so key to life that the
genes for these regulatory proteins have been highly conserved
through
evolution
the genes are basically the same in yeast, insects, plants & animals (including humans)Slide23
External signals
Sometimes the signals are EXTERNAL…
Growth
factors
Proteins or steroid hormones
that bind to
receptors
on the cell surface, with the primary result of activating cellular proliferation
and/or
differentiation
.
Many growth factors are quite versatile, stimulating cellular division in numerous different cell types; while others are specific to a particular cell-type
Allow coordination
between cells
density-dependent
inhibition
crowded cells stop dividing
When not enough growth factor left to trigger division in any one cell, division stops
anchorage dependence
to divide cells must be attached to a substrate or tissue matrix
“touch sensor” receptorsSlide24
Cancer & Cell Growth
Cancer is essentially a failure
of cell division
control
unrestrained, uncontrolled cell growth
What control is lost?
lose checkpoint
stops
gene
p53
plays a key role in G
1
restriction point
p53 protein halts cell division if it detects damaged DNA
options:
stimulates repair enzymes to fix DNA
forces cell into G
0
resting stage
keeps cell in G
1
arrest
causes apoptosis of damaged cell
ALL
cancers have to shut down p53 activity
p53 is the
Cell Cycle
EnforcerSlide25
Development of Cancer
Cancer
develops only after a cell experiences ~6 key
mutations
(“hits”)
unlimited growth
turn
on
growth promoter genes
ignore checkpoints
turn
off tumor suppressor genes (p53)
escape apoptosis
turn
off
suicide genes
immortality = unlimited divisions
turn
on
chromosome maintenance genes
promotes blood vessel growth
turn
on
blood vessel growth genes
overcome anchor & density dependence
turn
off
touch-sensor gene
It
’
s like an
out of control
car
!Slide26
What causes these “hits”?
Mutations in cells can be triggered by
UV radiation
chemical exposure
radiation exposure
heat
cigarette smoke
pollution
age
geneticsSlide27
Tumors
Mass of abnormal cells
Benign tumor
abnormal cells remain at original site as a lump
p53 has halted cell divisions
most do not cause serious problems &
can be removed by surgery
Malignant tumors
cells leave original site
carried
by blood & lymph system to other tissues
start more tumors =
metastasis
impair functions of organs throughout bodySlide28
Traditional treatments for cancers
Treatments target rapidly dividing cells
high-energy radiation
kills rapidly dividing cells
chemotherapy
stop DNA replication
stop mitosis & cytokinesis
stop blood vessel growthSlide29
Time for your
oncology rotation!
You are medical school students on an oncology rotation
Choose a narrator, scribe and
researcher
Start with the “Mystery” – when you have answered the questions, raise a hand for your supervisor to check in with you (yes, that is me)
You must check in with me before proceeding to each new portion of your case study.
Your group’s grades will be based on our discussions – everyone must be prepared to answer the supervisors questions!