Unit 6 - The Cell Cycle
• The white sections summarize key information and
vocabulary terms are underlined.
What is the cell cycle?
• Much as your body goes
through different stages in
your life, the cells and viruses
do too.
• The life cycle of the cell is
known as the cell cycle.
• In this unit we will discuss the
of the cell cycle (the process
of making of new cells).
http://www.wadsworth.org/BMS/SCBlinks/
mcewen/Media/fig_1_cell_mitosis.jpg
5 Reasons Cells Divide
1. Growth- an organism will increase in size as the
number of cells making up that organism increase
2. Differentiation- cells develop specialized cells to
carry out specific tasks
ex: the heart cell versus the muscle cell
3. Repair- to repair lost or damaged cells
ex: mending of skin, blood vessels and bone
4. Regeneration- ability to replace a lost limb or body
part by rapid cell division ex: starfish, lizard
5 Reasons Cont.
• And finally…
5. Reproduction – the making of a new organism
http://ghr.nlm.nih.gov/handbook/illustrations/mitosismeiosis;jsessionid=B368026AB01
E981849F2E31603F7154F
Cell Division
• The splitting of a single cell into two new daughter cells
is called cell division.
• This will occur when a cell reaches it’s maximum size
and the nucleus initiates cell division; proteins called
cyclins and enzymes begin this process.
http://protist.i.hos
ei.ac.jp/PDB/Ima
ges/Sarcodina/H
eliozoa/Actinosph
aerium/cell_divisi
on_1.jpg
Two Types of Cell Division
• Mitosis- the division of
body cells (AKA somatic
cells) due to the splitting
of the nucleus to create
two new cells.
• Meiosis – the creation of
gametes (AKA sex cells)
by cutting the # of
chromosomes in half to
create sex cells.
http://ghr.nlm.nih.gov/handbook/illustrations/mitosi
smeiosis;jsessionid=B368026AB01E981849F2E3
1603F7154F
Chromosomes
• Review: We have already
learned that genetic information
is held within the nucleus (of
eukaryotes) in the form of DNA.
• Therefore, it is very important
that cells must copy their
genetic information before
dividing.
• Cells tightly coil their DNA into
chromosomes during the
process of mitosis.
http://www.koshland-sciencemuseum.org/exhibitdna/images/
dna/intro02.gif
Chromosomes Cont.
http://www.learner.org/channel/courses/biology/images/archive/fullsize/1940_fs.jpg
Chromosomes Cont.
• During mitosis, identical
chromosomes pair up and
are now called sister
chromatids (1), held
together by a centromere
(2).
• Sketch it!
http://upload.wikimedia.org/wikipedia/e
n/5/54/Chromosome.png
Stage #1
Interphase
1.
•
•
http://dedunn.edublogs.org/files/2011/06/mi
tosis-26hzktr.jpg
•
Interphase = The period of
growth for the cell before cell
division (the longest stage)
which is broken up into the
following phases:
G1 – growth and
development organelles
copied
–
After G1 cells typically
enter a resting phase, G0
S – synthesis phase; copies
of the DNA
G2 – more growth
Knowledge Check
During the course of
the life of a cell,
there is a
complicated series of
checkpoints to
ensure that
everything is going
according to plan.
When something
happens to the
genes for these
“checkpoints”,
cancer can develop.
2.
•
•
Prophase = The
beginning of M phase
[mitosis] DNA
condenses and forms
chromosomes
Identical chromosomes
(Xsomes) join
Nucleus disappears
• Centrioles (the organelles which form the spindles)
move to opposite poles
• Spindle fibers (long strings that help the cell divide)
begin to grow
http://dedunn.edublogs.org/files/2011/06/mi
tosis-26hzktr.jpg
Stage #2
Prophase
Stage #3
Metaphase
3.
•
Metaphase =
Xsome pairs line up
along the middle of
the cell on the
metaphase plate
Centrioles have
moved to the poles;
spindle fibers
attach to Xsomes.
http://dedunn.edublogs.org/files/2011/06/mitosis26hzktr.jpg
Metaphase Cont.
http://student.ccbcmd.edu/courses/bio141/lecguide/unit6/genetics/DNA/DN
Arep/images/metaphase1_pc.jpg
Stage #4
Anaphase
http://dedunn.edublogs.org/files/2011/06/mitosis-26hzktr.jpg
4.
•
Anaphase = The centromeres divide and spindle fibers
pull the chromosomes apart from their partners
The chromatids move to opposite poles of the cell
Stage #5 Telophase
5.
•
•
•
Telophase = The
nuclei reform at each
end of the cell
Chromosomes uncoil
into chromatin (or
loose genetic material)
Spindles release
Xsomes and shorten.
The cell begins to
pinch as the cytoplasm
begins to divide
http://dedunn.edublogs.org/files/2011/06/mitosis26hzktr.jpg
Stage # 6 Cytokinesis
6.
•
•
•
Cytokinesis = The final stage in M
phase that divides the cell cytoplasm
– In animals, the cell membrane is
drawn inward (cleavage furrow).
– In plants, a cell plate is built to
create new cells walls and
membranes.
Each half has one nucleus and gets
own set of centrioles (+ organelles)
The cell is now two and enters
Interphase (G1).
Animation
http://alevelnotes.com/content_image
s/i77_dwa_1_mitosis.gif
Cytokinesis Cont.
•
“During mitosis, after all the genetic material is sorted
out, the cell splits all of its cytoplasmic goodies in two
and sends them to opposite ends. It then constricts in
the middle and eventually ‘pinches’ in half, producing
two daughter cells. The location at which the pinching
in occurs is known as the cleavage furrow.” Image
Visualizing Mitosis
Anaphase
Prophase
Interphase
Metaphase
http://wiki.district87.org/images/9/9f/Plant_cells.jpg
Telophase
Ex Mnemonics
• Example:
I = “I
P = please
M = make
A = another
T = two
C = cells!”
• Student Created Example:
I = “Intelligent
P = people
M = make
A = all
T = the
C = cash!”
http://buffonescience9.wikispaces.com/file/view/Mitosis-Animation1.gif/294684052/236x228/Mitosis-Animation-1.gif