1. Cell Division
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2. Why Cells Make More Cells
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Why Cells Make More Cells
1. Most cells go through a series of changes in order to maintain homeostasis.
2. Cells need to reproduce (divide) when their surface area can no longer supply the much larger volume with nutrients and get rid of wastes.
Surface Area (length x width x 6)
Volume
(length x width x height)
Ratio of Surface Area to Volume

3. Introduction to Mitosis
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1. Two main stages of cell division
a. Mitosis: division of the nucleus
b. Cytokinesis: division of the cytoplasm
2. Produces 2 cells called daughter cells
a. Cells are genetically identical
3. Mitosis is source of new cells for
a. Growth
b. Development
c. Repair
d. Replacement of old cells
Normal red blood cells only live for 120 days. Then they die & stem cells make new ones.
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4. Fruit flies have 8 chromosomes in each body cell
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1. Chromosomes: made up of DNA & proteins
2. Carry the cell’s coded genetic information
3. Different organisms have a different number of chromosomes
Fruit flies have 8 chromosomes in each body cell
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Humans have 46 chromosomes in each body cell
Frogs have 26 chromosomes in each body cell

5. Vocabulary 1. Chromatin: the relaxed, uncoiled state of the chromosome
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1. Chromatin: the relaxed, uncoiled state of the chromosome
2. Chromatid: one of two identical “sister” parts of a duplicated chromosome
Chromosome: threadlike structures within the nucleus containing genetic information that is passed on from generation to generation
4. Centromere: chromosome region that joins 2 sister chromatids

6. Cell Cycle Consists of 2 phases M phase: Mitosis & Cytokinesis
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1. Cell cycle: Sequence of events between the time a cell divides to form 2 daughter cells & the time those 2 cells divide
Consists of 2 phases
M phase: Mitosis & Cytokinesis
Interphase G1 S G2

7. Mitosis Discovered
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Walther Flemming first discovered mitosis in 1870 and reported is discovery of chromosomes and mitosis in 1882.
Metaphase in a salamander cell
drawn by Walther Flemming from a stained slide.

8. Interphase: 3 Phases 1. G1 phase: Growth Phase
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centrioles
1. G1 phase: Growth Phase
Cell performs all life’s activities: protein synthesis, waste removal, organelle synthesis, etc.
2. S phase: DNA Replication
DNA makes a copy of itself
Produces 2 identical sets of chromosomes
3. G2 phase: Preparation
Cell produces centrioles & spindle fibers needed to move the chromosomes
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Nucleus & duplicated chromosomes

9. Mitosis Described as movement of chromosomes
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Mitosis
Described as movement of chromosomes
Continuous series of events
Divided into four phases so that it is easier to understand
Cell Cycle

10. Prophase: 1st Phase
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1. Chromatin (DNA) condenses, coils, & becomes rod shaped
2. Centrioles move to opposite ends of cell
3. Spindle fibers attach to chromosomes
4. Nuclear membrane breaks down

11. Metaphase
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1. Spindle fibers push & pull chromosomes until they line up across center of cell
2. Centromere of each chromosome pair is attached to a spindle fiber
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12. Anaphase 1. Spindle fibers shorten & paired chromatids separate
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1. Spindle fibers shorten & paired chromatids separate
2. Spindle fibers pull separated chromosomes to opposite ends of the cell
3. Centromere of each pair divides; now have individual chromosomes
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13. Telophase 1. Chromosomes begin to uncoil and de –condense
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1. Chromosomes begin to uncoil and de –condense
2. Nuclear membrane reforms around each new set of chromosomes
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14. Cytokinesis 1. Cytokinesis is division of the cytoplasm
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Cytokinesis
1. Cytokinesis is division of the cytoplasm
2. Distributes the organelles
In animal cells, the cell membrane pinches together around the middle of the cell and forms 2 cells.
In plant cells, a cell plate forms across the middle of the cell and new cell walls form between the daughter cells
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15. Cancer Cells
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1. Normal cells contain check points to regulate the cell cycle, & stop at appropriate check points.
2. Cancerous cells do not respond to check points and continue rapidly through the cell cycle. This results in masses of undefined cells called tumors.
3. Cancer cells do not mature; they become more immature.

16. Binary Fission
1. Binary fission is the process by which all bacteria reproduce .
Each resulting daughter cell is genetically identical to the parent cell.
3. Under ideal conditions, bacteria can reproduce once every 20 minutes
If you start out with 1 bacterium cell, how many could be produced after 7 hours?
2, 097, 152 produced in just 7 hours!