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22 Cards in this Set
- Front
- Back
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In unicellular organisms ...
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division of one cell reproduces the entire organism
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Multicellular Organisms depend on cell division for:
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-Growth and Development
-Repair (tissue renewal) |
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Cell Division results in
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2 daughter cells with identical genetic information (DNA)
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Chromosomes
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where DNA molecules are "packaged"
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Somatic Cells
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(nonreproductive cells) have two sets of chromosomes
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Gametes
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(reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells
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Step 1 of Distribution of chromosomes during eukaryotic cell division
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chromosomes condense, DNA is replicated, chromosomes are duplicated
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Step 2
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Each chromosome exists as two sister chromatids
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Step 3
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The centromere is the narrow "waist" of the duplicated chromosomes where the chromatids are most closely attached
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Step 4
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The chromatids are pulled apart into 2 chromosomes and distributed in 2 daughter cells
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Mitosis
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division of the nucleus
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Cytokinesis
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the division of the cytoplasm
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The cell cycle consists of 2 main phases
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Mitotic Phase (mitosis and cytokinesis)
Interphase (cell growth and copying of chromosomes in preparation for cell division) |
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Interphase and its subphases
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G1 phase ("first gap")
S phase ("synthesis") G2 phase ("second gap") Cell grows during all three phases. Chromosomes are duplicated only during S phase. |
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Mitosis is conventionally divided into five phases.
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Prophase
Prometaphase Metaphase Anaphase Telophase |
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Interphase
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-intact nuclear envelope
-2 centrosomes formed -chromosomes duplicated in S phase -chromosomes not condensed |
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Prophase
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-duplicated chromosomes condense
-sister chromatids joined together at centromere -formation of mitotic spindle and asters -centrosomes move away from each other |
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Prometaphase
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-nuclear envelope fragments
-centrosomes can now invade the nuclear area -kinetochores form at the centromeres of chromatids -microtubules attach to the kinetochores -kinetochore microtubules tug on the chromosomes -nonkinetochore microtubules bind to each other |
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Metaphase
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-longest stage of mitosis
-centrosomes at opposite poles -chromosomes gather on the metaphase plate -each x-some attached to kinetochore microtubules |
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Anaphase
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-shortest stage of mitosis
-cohesin proteins cleaved -chromosomes begin to separate -chromosomes pulled toward centrosome -nonkinetochore microtubules lengthen the cell -each end of the cell now has a complete set of x-somes |
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Telophase and Cytokinesis
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-2 daugheter nuclei form in the cell
-x-somes become less condensed -mitosis now complete -2 cells form by cytokinesis |
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Cell Cycle Control System
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(analogous to a clock)
-regulated by both internal and external controls -the clock has specific checkpoints where the cell cycle stops until the go ahead signal is received. |
