Transcript Size, DNA, nuclear envelope** The Cell Cycle Clock

Do Now: We have spent the spent the
majority of the year exploring the
molecules that are used by and
construct cells. We have discussed
ways those materials interact in
metabolic processes in individual cells
and how messages are passed between
cells. Think about an individual cell –
any cell in your body – what does its
life cycle look like from “birth” to
“death.” Discuss your ideas with a
partner and create a model to show
where this cell came from, what it
does on a daily basis, and ultimately
how it dies (be mindful of time).
If the life cycle of a cell was a
clock…
G1 – Growth
& metabolism
S – DNA
replicated for
cell division
G2–
Additional
growth & prep
for division
Where is all of the information kept
that allows this cycle to occur at all?
What is the molecule that is stored
there?
Brainstorm! What DNA’s purpose? What
does it “tell” the cell to do? How does
DNA relay this information to the cell?
What does this look like? Draw a diagram
to illustrate your ideas. Can this
information sharing ever be disrupted? By
what? What do you think the implications
would be? Provide a specific example
based on your brainstorming ideas.
Reviewing
the
Cell Cycle
Which phase are
most cells in? What
can you conclude
about the stage cells
spend most of the
their life in?
Two Periods
1. Growth
Interphase
Size ↑
Metabolism
Chromosomes
copied
2. Division
Mitosis
2 daughter cells
formed
Cytokinesis
Cytoplasm
divides
**Size, DNA, nuclear envelope**
The Cell Cycle Clock
Interphase
Longest period
3 phases:
1. G1 – cell grows and develops;
chromosomes unclear
During G1 the cell receives 1 of 2
signals:
1. Mature – no more division
2. Divide (restriction point,
R): prepare for mitosis
2. S – DNA rep,
form sister chromatids
connected by centromere
3. G2 – chromosomes
condense, proteins &
organelles made to prep
for division
Mitosis
FOUR stages → 2 identical cells
Prophase
Longest phase
Chromatin coils to chromosomes
Nuclear envelope begins to
disappear – nucleolus disintegrates
Centrioles migrate to opposite ends
Spindle fibers appear between
centrioles
Metaphase
Short second phase
Spindle fibers attach at centromere
Chromosomes line up at equator
Each chromatid attached to own
spindle fiber – 1 at one pole, 1 at the
other
Anaphase
Separation of sister chromatids
Centromeres split, pair separated
Chromatids pulled apart as spindle
fibers shorten
Telophase
Chromatids reach opposite ends
Start to unwind
Spindles break down
Nucleolus reappears, nuclear
envelope develops – membrane
reforms
Cytokinesis
Division of cells
Animal cells – pinch at equator
Plant cells – “plate” laid around
sister cells, 2 cell walls form
Controls at multiple points make sure
the process is occurring correctly!
Cells out of
control!
Result in outgrowths - tumors
2 types: BENIGN &
MALIGNANT
Benign tumors push structures out
of the way
Malignant tumors are
CANCEROUS!!
Common Types of Cancer
Lung
Liver
Colon
Skin
Cervical
Ovarian
Breast
•Influenced by
biological and
environmental factors
• Common treatment
•paths
Difficult
to detect.
– surgery
and
Risks
increase with
chemo/radiation
age; therapy
symptoms
include abdominal
pains & swelling,
fatigue
• Treatment usually
includes surgery &
chemotherapy