Cell Division
Why Study Cell Division?
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Development
Limb regeneration
Stem cells/stem cell therapy
Virology
Cancer
Cancer
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Loss of cell division control leads to
unlimited division --- cancerous tumors
Oncogenes are proteins that increase the
chances of a normal cell becoming a
cancer cell
Many viral proteins are oncogenes and
links between virus infection and cancer
have been found
Cancer
http://www.nature.com/nrm/journal/v9/n8/box/nrm2457_BX1.html
Cell Division
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All cells arise from previously existing
cells.
New cells are produced for growth or to
replace damaged or old cells.
Cell division differs between prokaryotes
and eukaryotes (binary fission vs. mitosis).
Cell division differs in asexual and sexual
replication (mitosis vs meiosis).
Genetic Fidelity
DNA contains all the
information about cell
function so each new cell
must receive a complete,
accurate copy of DNA during
cell division. This ensures
two identical daughter cells
are produced.
Prokaryotic DNA
In prokaryotes, a
large circular
chromosome is
bound to the
plasma membrane.
Smaller plasmid
DNA may also be
present.
Chromosomes
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Eukaryotic cells contain large amounts of genetic
material.
 The human cell contains more than 3 meters
of DNA!!!
This DNA is packaged into structures called
chromosomes located in the cell nucleus.
 Most eukaryotes contain between 10 and 50
chromosomes.
 Humans have 23 pairs (46) chromosomes.
Chromosome Structure
DNA is wrapped
around proteins
called histones.
http://cyberbridge.mcb.harvard.edu/dna_2.html
http://www.mun.ca/biology/desmid/brian/BIOL2060/BIOL2060-18/CB18.html
Chromosome Structure
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In nondividing cells,
chromosomes are more
loosely packed and
called chromatin.
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In dividing cells,
chromosomes
condense into tightly
packaged
chromatids.
Chromatids
After DNA replication, the
pair of sister chromatids
are joined at the
centromere.
http://www.uic.edu/classes/bios/bios100/lectures/mitosis.htm
http://www.macroevolution.net/sister-chromatids.html
Karyotype
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http://scigjt13.wordpress.com/2011/03/02/karyotype-of-alzheimers-disease/
Human chromosomes
are paired and
arranged by size in
karyotypes.
The first 22 pairs are
autosomes.
The final chromosome
pair is the X/X or X/Y
sex chromosomes.
Cell Reproduction
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Asexual reproduction creates 2 diploid
daughter cells that are identical to the parent
cell.
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Binary fission (prokaryotes);
Mitosis (eukaryotes)
Sexual reproduction creates daughter cells
that are not genetically identical to the parent
cell.
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Meiosis
Prokaryotic Cell Reproduction
Binary Fission
Binary Fission
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http://academic.pgcc.edu/~kroberts/Lecture/Chapter%206/fission.html
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Prokaryotes
divide by
binary
fission.
Circular DNA
chromosome
(and
plasmids)
replicates.
Cell wall
forms
creating two
new, smaller
cells.
Animation
Eukaryotic Cell Cycle
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Two Stages of Eukaryotic Cell Cycle
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Interphase
G1 – Primary growth phase
 S phase – DNA synthesis
 G2 – Secondary growth phase
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Mitosis and Cytokinesis
The Cell Cycle
http://www.bristol.k12.ct.us/page.cfm?p=7094
The Cell Cycle
Interphase: The G1 Stage
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1st stage of growth for a new cell after
division
Cells mature (make more cytoplasm and
organelles).
Cells will carry out normal metabolic and
biological functions.
Interphase: The S Phase
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S for DNA
Synthesis
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DNA is replicated
to create 2
complete copies
of original
chromosomes
Interphase: The G2 Stage
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2nd stage of growth following DNA replication
Cell creates all organelles and proteins that will be
needed for cell division
 Example - centrioles
Interphase: Summary
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Newly formed cells grow in size and
make organelles/proteins needed to
perform function (G1).
Chromosomes replicate making 2
complete copies (S).
Cells make organelles and proteins
needed for mitosis (G2).
Mitosis
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Division of nucleus
Occurs in eukaryotes only
Consists of 4 steps:
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Prophase
Metaphase
Anaphase
Telophase
Does not occur in some cell types (nerve cells)
http://botit.botany.wisc.edu/Resources/Botany/Mitosis/Allium/Complete%20Mitosis.jpg.html
Mitosis – Early Prophase
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Chromatin condenses to form visible
chromosomes
Mitotic spindle forms from fibers in
cytoskeleton or centrioles
nucleolus
cell wall
chromatin
nuclear
envelope
http://mrteacherdude.com/biology/biology2/lab_stuff/mitosis/mitosis_plant_pro.htm
http://www.bristol.k12.ct.us/page.cfm?p=7094
Mitosis – Late Prophase
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Nuclear membrane and nucleolus are
broken down.
Chromatin continues to condense.
Kinetochores attach to centromeres.
Spindle forms at pole of cell.
http://mrteacherdude.com/biology/biology2/lab_stuff/mitosis/mitosis_plant_pro.htm
http://www.bristol.k12.ct.us/page.cfm?p=7094
Kinetochore and Spindle Fibers
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The mitotic spindle
forms from
microtubules in
plants and centrioles
in animals.
Polar fibers extend
from one pole of the
cell to the other.
Short asters radiate
from spindle.
http://en.wikipedia.org/wiki/Spindle_apparatus
http://en.wikipedia.org/wiki/Spindle_apparatus
Kinetochore and Spindle Fibers
http://en.wikipedia.org/wiki/Spindle_apparatus
Kinetochore fibers
extend from the pole to
the centromere of the
chromosome.
asters
pole
chromosomes
Mitosis - Metaphase
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Chromosomes attached to kinetochores
move to the center of the cell.
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Lined up at equator.
equator
pole
http://www.cbv.ns.ca/bec/science/cell/page17.html
http://www.bristol.k12.ct.us/page.cfm?p=7094
Mitosis - Anaphase
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Kinetochore fibers pull sister chromatids
apart.
Very rapid.
http://micro.magnet.fsu.edu/micro/gallery/mitosis/earlyanaphase.html
http://www.bristol.k12.ct.us/page.cfm?p=7094
Mitosis - Telophase
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Sister chromatids migrate to opposite poles.
Spindle disassembles.
Nuclear envelopes form around each set of sister
chromatids.
Nucleolus reappears.
Chromosomes return to chromatin.
Cytokinesis occurs.
http://botit.botany.wisc.edu/Resources/Botany/Mitosis/Allium/telophase%20cytokinesis.jpg.html
http://www.bristol.k12.ct.us/page.cfm?p=7094
Mitosis - Cytokinesis
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Division of cytoplasm between daughter
cells
In plants a cell plate forms at the
equator to divide cells.
In animals a cleavage furrow divides
cells.
Mitosis - Cytokinesis
Cleavage Furrow
http://www.uic.edu/classes/bios/bios100/lectures/mitosis.htm
http://kr021.k12.sd.us/mitosis_practice_test.htm
Cell Plate
http://www.vcbio.science.ru.nl/en/virtuallessons/mitostage/
Completion of Mitosis
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After mitosis you have 2
daughter cells that are
identical to parent cell in
chromosome number
and DNA sequence*.
Daughter cells are smaller
than mature cell and enter
G1 phase (interphase) to
grow and function.
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/mitosis/mitosis.htm
Mitosis
Mitosis Animation
Plant Cell Mitosis
Mitosis Review – Be able to sketch!
Mitosis Review – Be able to sketch!
Mitosis Review – Be able to label
stages and structures!
Mitosis Quiz
1. The 2 chromatid arms are held together
in the center by a _____________.
A. centrosome
B. centriole
C. centromere
D. histone
Mitosis Quiz
2. A cell with only one of each kind of
chromosome is said to be 1n or ______.
A. diploid
B. cancer
C. haploid
D. mitotic
Mitosis Quiz
3. Which of the following shows the correct
order for the phases of the cell cycle?
A. G1 – G2 – S – M
B. S – G1 – M – G2
C. G1 – S – G2 – M
D. G1 – M – G2 - S
Mitosis Quiz
4. The diagram shown is a
picture of a person’s
chromosomes called a
_______.
A. karyotype
B. genome
C. chromatid
D. centromere
5. The person shown is _____
A. Male
B. Female
Mitosis Quiz
6. Cells spend most of their time in this
stage of the life cycle.
A. Interphase
B. Mitosis
C. Telophase
D. Anaphase
Mitosis Quiz
7. The place where the cell
membrane pinches in to
make 2 new daughter cells
is called the _______.
A. cleavage furrow
B. cell plate
C. pole
D. kinetochore
Mitosis Quiz
Which of the pictures
shows:
8. Metaphase?
9. Telophase?
10. Prophase?
11. Anaphase
A.
C.
B.
D.