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Mitosis: Cell Division
• DNA – made of nucleic acids, housed in the
nucleus, contains genes
• Chromatin – long strands of DNA that are
wrapped around proteins (histones)
• Nucleosome – the DNA/ histone complex
Why does mitosis happen?
• Surface area to volume ratio
– As a cell grows, the volume grows faster than
the surface area
– Not enough space in the cell membrane to send
wastes out or to bring food in
• Signal is sent to the cell
– An organism needs to grow
– To repair damage
Structure of a Chromosome
•Chromosome – a structure that is
made of DNA and the proteins
associated with it
•Chromatid – one of the 2 exact
copies of the DNA – often referred
to as “sister chromatids” – the 2 of
them together make a chromosome
•Centromere – the point where the
2 chromatids are connected
together to make a chromosome
Homologous Chromosomes
•two chromosomes that code for the same
traits. One is from mom the other is from
Cell Cycle
• Interphase
– Majority of a cell’s life
– Cell grows
– Chromosomes duplicate
• Mitosis
– Creates 2 daughter cells
that are identical to the
parent cell
– Cell division
• G1
– Growth One
– The cell spends most of its life
• S
– Chromosomes are duplicated
• G2
– Organelles and other parts needed for cell
division are duplicated
• Prophase – the chromosomes
become visible – the nuclear
envelope disappears – pro = first
• Metaphase – the chromosomes
line up in the middle of the cell
• Anaphase – the sister chromatids
move away from each other
• Telophase – begins as chromatids
reach opposite ends of the cell
• The cytoplasm and organelles are divided
between the two sides
• Plants:
– A cell plate begins forming
• Animals:
– A cleavage furrow forms as the
cell pinches inward
Levels of Organization
Organ Systems
When Good Cells Go Bad!
Facts about cancer
• Who will develop it?
– ½ of men and 1/3 of women in the U.S. will
develop cancer in their lifetime
• What is it?
– Uncontrolled cell division
• What causes the cell to keep dividing?
– Failure to produce internal regulators or respond
to external regulators
Causes of Cancer
• a. Tobacco use – lung, mouth, esophageal,
cervical cancer
• b. Asbestos – lung cancer
• c. Radiation exposure
• d. Viral infection - HPV
• e. Charred meat – colon cancer
• f. Genetic
• g. Chemical exposure
• h. UV exposure (sun or tanning bed) – skin
• i. Drinking more than one drink a day for women
or 2 a day for men
Kinds of Cancer
• Metastatic
– More dangerous
– Cancer travels in the
• Nonmetastatic
– Usually less dangerous
– Cancer does not travel
Not all cancers form tumors and not all tumors are cancerous!
How does cancer spread?
Pancreatic Cancer