 CELL REPRODUCTION
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BEGINS WITH REPLICATION (DUPLICATION) OF DNA
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THESE REPLICAS BECOME THE DNA IN THE TWO NEW DAUGHTER CELLS
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DNA NUCLEOTIDES ARE “PROOF-READ”; WHEN A MISTAKE IS MADE—MUTATION
Chromosomes & their Replication
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Human cell contains 46 chromosomes, arranged in 23 pairs
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Protein HISTONES packages DNA tightly
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Newly formed chromosomes attached at a point called centromeres
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The duplicated but still attached chromosomes are called chromatids
CELL MITOSIS
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PROCESS BY WHICH THE CELL SPLITS INTO TWO
STEPS: SHORTLY BEFORE MITOSIS, TWO PAIRS OF CENTRIOLES BEGIN TO MOVE APART FROM
EACH OTHER FORMING SPINY STAR-SHAPE (ASTER). SOME SPINES PENETRATE THE NUCLEAR
MEMBRANE. TOGETHER WITH THE SPINDLE, THEY FORM THE MITOTIC APPARATUS
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INTERPHASE
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Before a dividing cell enters mitosis, it undergoes a period of growth called interphase.
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Some 90 percent of a cell's time in the normal cellular cycle may be spent in interphase.
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G1 phase:
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The period prior to the synthesis of DNA.
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Cell increases in mass in preparation for cell division.
S phase:
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G2 phase:
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Period during which DNA is synthesized.
Period after DNA synthesis has occurred but prior to the start of prophase.
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Cell synthesizes proteins and continues to increase in size.
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In the latter part of interphase, the cell still has nucleoli present.
MITOSIS
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Prophase
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Spindle is forming
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Chromosomes become condensed into well-defined chromosomes
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Kinetochores, which are specialized regions in the centromeres of chromosomes, attach to a type of microtubule
called kinetochore fibers.
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Pro-metaphase
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Fragmentation of the nuclear membrane
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Microtubules from aster attach to chromatids at center
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Tubules pull one chromatid toward cellular pole and partner to opposite pole
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Metaphase
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Actin slides the spines in a reverse direction along each other
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Chromatids pulled to form the equatorial plate
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Remember this stage by thinking of M as in middle
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Anaphase
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Once the paired sister chromatids separate from one another, each is considered a "full"
chromosome. They are referred to as daughter chromosomes
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Two chromatids of each chromosome are pulled apart at the centromere
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The 46 pairs of chromatids are separated forming two separate sets of 46 daughter
chromosomes
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Remember this stage by remembering A representing AWAY
Telophase
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Two sets of daughter chromosomes are pushed completely apart
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Mitotic apparatus dissolves
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New nuclear membrane develops around each set of chromosomes
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Cell pinches in two caused by formation of a contractile ring (composed of actin and
myosin)
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Remember this stage by remembering T representing TWO
Cytokinesis
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The division of the original cell's cytoplasm
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Begins prior to the end of mitosis
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Completes shortly after telophase/mitosis.
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At the end of cytokinesis, two genetically identical daughter cells are produced