The Cell Cycle -life cycle of a cell Interphase (G1 + S + G2) - the beginning of the cell cycle -when the cell its busy doing its job, carrying out its function Interphase is the growth phase of a cell -cells spend most (about 75 to 80%) of their life in Interphase -cells grow in size and carry out metabolic functions -cells also prepare for mitosis in Interphase Interphase prepares for Mitosis: -duplicating DNA/ chromosomes duplicate (S phase) -synthesize proteins associated with DNA -double up organelles -synthesize structures used in mitosis and cytokinesis Mitosis (M phase): PMAT (4 phases) 1. Prophasethe first and longest phase of mitosis During prophase the sister chromatids (chromosome pair) become thicker (visible with light microscope) -nucleus and nuclear envelope disappear -microtubules and spindle fibers (they will pull sister chromatids apart in anaphase) assemble -in animal cells centrioles move to the end of the cell 2. Metaphase-shortest phase -chromosomes move to the spindle equator (middle of the cell) -spindle fibers attach to centromeres ( tie holding sister chromatids together) 3. Anaphase-the centromeres of each chromosome are pulled apart by the spindle fibers - the sister chromatids are pulled toward the opposite end of the cell so they will be separated equally into each new cell 4. TelophaseThe chromatids are now at opposite ends of the cell -many of the steps in prophase will reverse - the nucleus and nucleus reappear; except now there are two of each at each end of cell -the chromosomes (separated chromatids) begin to thin out by unwinding and began to direct the cells metabolic activity -the spindle fibers break down -the plasma membrane begins to reform (cytokinesis begins) Cytokinesis – division of the cytoplasm when one cell splits completely into two new cells In animals cell the membrane pinches in half (cleavage furrow) In plant cells – a new cell wall is built (cell plate)
