Transcript Mitosis and Cancer

MITOSIS
What is Mitosis?
• Cell Division
• The division of a single
nucleus into two identical
daughter cells
Why do cells go through
mitosis?
• Growth
• Repair/replacement
• Reproduction
Chromosomes
• Are made up of
genes
• Genes are made
up of DNA
• DNA is made up
of nucleotides
How many chromosomes do humans
have?
• 46 chromosomes
• Chromosomes
are only visible
during cell
division
Chromosome Structure
• Before cell division,
chromosomes replicate
• Each chromosome
consists of two identical
“sister” chromatids
What would need to
happen before a cell
could divide?
Copy it’s genetic AND
cellular material
Cell Cycle
• Interphase
– In between cell divisions
– Three parts (G1 phase, S phase, G2
phase)
• Mitotic Phase
– Mitosis
• Four Parts (Prophase, Metaphase,
Anaphase,Telophase)
– Cytokinesis
Interphase
G1 phase
• Most growing occurs;
cells increase in size
• New proteins and
organelles are made
Interphase
S phase
• Chromosomes are
replicated
• Synthesis of DNA takes
place
• Proteins associated with
chromosomes are made
Interphase
G2 phase
• Shortest phase
• Organelles
(centrioles) and
molecules needed
for mitosis are
made; checks for
necessary repairs to
the DNA
Mitosis
• Prophase
– 50-60% of time required for mitosis
– Chromosomes become visible
– Centrioles go to opposite poles
– Chromosomes attach to spindle
fibers
– Nucleolus disappears
– Nuclear envelope breaks down
Mitosis
• Metaphase
– Lasts only a few minutes
– Chromosomes line up across the center of
the cell
– Microtubules connect the centrosome of
each chromosomes to the poles of the
spindle
Mitosis
• Anaphase
– Centrosomes that join sister chromatids
separate
– Each sister chromatid becomes an
individual chromosome
– Chromosomes (sister chromatids) move
to opposite poles
Mitosis
• Telophase
– (reverse of prophase)
– Chromosomes spread out and become a
tangled dense mass of chromatin
– Nuclear envelope reforms
– Spindles break apart
– Nucleolus becomes visible
Cytokinesis
• “division of cytoplasm”
• In animal cells, cell membrane pinches in
(“cleavage furrow”) separating the cell into
two equal parts
• In plant cells,
– a cell plate forms down the middle of the
cell
– Cell plate gradually becomes a separating
membrane
– A cell wall forms in the cell plate
Mitosis Video
• http://www.youtube.com/watch
?v=VlN7K1-9QB0
What phase of mitosis is shown in each
picture?
Cell Cycle Pictures in Order
What affects Cell Division?
• Anchorage
– Animal cells must be in contact with a solid
surface to divide
• Cell density
– Crowded cells stop dividing
• Chemical growth factors
– Proteins secreted by body cells that stimulate
other cells to divide
Cancerous Cells
• Don’t
– react to normal control
mechanisms
– respond to regulatory
signals that are part of
the cell cycle
– exhibit densitydependent (contact)
inhibition
– stop dividing when
growth factors aren’t
available
What is cancer?
• Uncontrolled mitosis
(cell division)
• Metastasis: spread of
cancerous cells
• Immortal (normal
cells can only divide
~50 times before
dying)
Cancer Video
http://www.youtube.com/wat
ch?v=LP52CyYmY_U&N
R=1
Chemotherapy Video
http://www.youtube.com/wat
ch?v=tYABZdpsC9M&N
R=1
What causes cancer?
• Normally, tumor suppressors
genes send messages to kill
damaged cells
• If tumor suppressor genes
malfunction, some damaged
cells
– will die off
– divide uncontrollably and give
rise to cancer.
• Oncogenes
– mutated genes will cause cancer
What damages the DNA?
• Carcinogens – agents that cause mutations
in the DNA
• Ex. radiation, hormones, viruses, and many
chemicals
Why are cancers so dangerous?
• Cancers
– displace and put
pressure on normal
tissues
– cut off blood supply
to normal tissues
– interrupt organ
function
Resources
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http://www.healthsystem.virginia.edu/internet/huntdisease/images/DNA.gif
http://www.nia.nih.gov/NR/rdonlyres/E2CBDDA6-4658-485B-B63C-14E7159C74B7/0/DNA_LOW.JPG
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http://imagecache2.allposters.com/images/pic/JAG/03-PS101-5~Mitosis-Posters.jpg
http://www.stanford.edu/group/hopes/basics/dna/f_b11homolgs.jpg
http://www.cbp.pitt.edu/faculty/yong_wan/images/main_cell_cycle.jpg
http://www.le.ac.uk/ge/genie/vgec/images/cellcycle.png
http://img.tfd.com/dorland/arm_chromosome.jpg
http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/Bio%20101%20Lectures/Mitosis/human_ch
romosomes_female_X_1000_1.jpg
http://www.mun.ca/biology/scarr/F14-10_FISH_chromosome.jpg
http://library.tedankara.k12.tr/chemistry/vol1/biochem/trans98.jpg
http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/mitosis/images/interphase1_pc.jpg
http://student.ccbcmd.edu/~gkaiser/biotutorials/dna/mitosis/images/interphase_ac.jpg
http://images.google.com/imgres?imgurl=http://www.ias.unt.edu/~tpp001/interphase_text.JPG&imgrefurl=http://www.
ias.unt.edu/~tpp001/Mitosis_Diagram_Page.main.html&usg=__kRmHOyZqZ32q2kyUCdW_pjupMH8=&h=327&w=
417&sz=27&hl=en&start=5&tbnid=8POhgQsjCqBR8M:&tbnh=98&tbnw=125&prev=/images%3Fq%3Dinterphase%
26gbv%3D2%26hl%3Den
http://www.ndpteachers.org/perit/Mitosis%5BAnimalCell%5D.GIF
http://www.youtube.com/watch?v=VlN7K1-9QB0
http://www.alternative-cancer.net/images/Cancer_cell,%20brain.jpg
http://assets.aarp.org/external_sites/adam/graphics/images/en/19349.jpg
http://whyfiles.org/coolimages/images/csi/HPV_small.jpg
http://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/RadiationPenetration2-pn.png/300pxRadiationPenetration2-pn.png
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