Cell Growth & Division
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Transcript of Cell Growth & Division
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Cell Growth & Division
Mitosis
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Why do Cells Reproduce?
• Growth of an organism
• Replacement of old or damaged cells
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Chromosomes• Each cell has lots of DNA, but it must be
condensed in order to fit in the nucleus
• DNA is organized and packaged into structures called chromosomes
• Prokaryotic Chromosome:
– Single circular strand of DNA that is condensed through many twists
• Eukaryotic Chromosome…
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Eukaryotic Chromosomes• Most eukaryotes have between 10 & 50
chromosomes in their body cells, but…
• Chromosomes can’t be seen when cells aren’t dividing and are called chromatin
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Eukaryotic Chromosomes• When cells are ready
to divide, the chromatin condenses into chromosomes
• Each of the 2 thick strands is called a chromatid
• Identical chromatids (sister chromatids) are held together at centromere
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Preparing for Cell Division• All newly-formed cells require DNA, so
before a cell divides, a copy of DNA is made for each new cell (daughter cell)
• This assures that new cells will work in the same way as the cells they came from
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• In prokaryotic cells, it’s simple!! DNA is copied, then cell divides
• In eukaryotic cells, it’s more complex…
Preparing for Cell Division
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Eukaryotic Cell Cycle: Overview 1.)
Interphase: when cell
grows and prepares to
divide
2.) Mitosis: when
nucleus divides
3.)
Cytokinesis: when cytoplasm divides and two new cells are complete
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Interphase• Growth stage
• Cells mature by making more cytoplasm
• Organelles and Centrioles duplicate
• DNA is copied
Two Two identicidentic
al al copies copies of DNAof DNA
Original Original DNADNA
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• Prophase
• Metaphase
• Anaphase
• Telophase
• PMAT!!
Mitosis
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Prophase• Chromatin in nucleus condenses to form
visible chromosomes
• Spindle fibers form from the centrioles and attach to centromeres
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Metaphase• Chromosomes that are attached to spindle
fibers move to the center of the cell and line up
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Anaphase• Occurs Rapidly
• Sister chromatids are pulled apart to opposite poles of cell by spindle fibers
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Telophase• Sister chromatids are at opposite poles
• Spindles disassemble
• Nuclear envelope forms around each set of sister chromatids
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Cytokinesis• Division of cytoplasm
• Division of cell into two, identical cells called daughter cells
• Daughter cells have the same # of chromosomes as each other and as the parent cell from which they were formed
• Must still grow in size to become mature
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Onion Root TipInterphase
Interphase
Prophase
Prophase
Prophase
Metaphase
Anaphase
Anaphase
Telophase
Cytokinesis
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Animation: