cell growth & division
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Cell Growth & Division. Mitosis. Growth of an organism. Replacement of old or damaged cells. Why do Cells Reproduce?. 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 - PowerPoint PPT PresentationTRANSCRIPT
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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: