Transcript 10.2 Cell Cycle

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10.2
Eukaryotic Cell Cycle
• Cell cycle--repeating phases of :
– Growth (Interphase)
– DNA replication (Interphase)
– preparation for cell division (Interphase)
– division of the nucleus and cytoplasm (cell
division—mitosis & cytokinesis)
Interphase
• G1: cell grows to mature size, makes
more organelles
• S: chromosomes replicate
• G2: cell continues to grow and prepare to
divide; cell forms specialized structures
that help the cell divide (ex. microtubules)
2 Stages of Cell Division:
1. Mitosis: the process in which a cell’s
nucleus divides into 2 identical daughter
nuclei.
*Begins after interphase and ends
before cytokinesis.
*PMAT (4 phases)
2. Cytokinesis: cytoplasm division (and
organelles)
*Cell physically splits into 2
MITOSIS — 4 phases (PMAT):
1. PROPHASE
• chromosomes condense (coil up and
become visible under a microscope).
• Centrosome helps to assemble
spindle fibers.
• a pair of centrioles migrate to each
pole of the cell (animal cells only).
• nuclear envelope and nucleolus break
down (disappear).
2. METAPHASE
• spindle fibers arrange chromosomes in the
middle of the cell along the equator of the cell.
• spindle fibers link the chromatids of each
chromosome to opposite poles.
3. ANAPHASE
• centromeres divide
• spindle fibers pull sister chromatids towards
opposite poles.
• result =each pole has a full set of chromosomes.
4. TELOPHASE
• 2 daughter nuclei are formed
• reverse of prophase: nuclear envelopes
form around each set of chromosomes;
chromosomes uncoil to form a loose mass
of chromatin; spindle fibers break down
(disappear).
CYTOKINESIS
• animal cell…cell membrane grows into
the center of the cell at the center of the
parent cell and divides it into 2
daughter cells of equal size; called a
cleavage furrow
• plant cells…form a cell plate (from the
parent cell wall).