Prophase
chromosomes condense and become visible under the light microscope; nucleolus disappears, nuclear envelope fragments; spindle assembly begins
Prometaphase
kinetochores appear at centrosomes; spindle fibers attach to chromosomes at kinetochores; motion is observed as the spindle fibers attach and pull on the kinetochores
metaphase
spindle fibers (attaches at kinetochores) pull chromosomes to the equatorial plane of the cell; visible as a line across the cell(called the metaphase plate)
anaphase
sister chromatids split apart at the centromere; spindle fibers (attached at kinetochores) pull daughter chromosomes to the opposite poles of the cell, the most visually exciting stage
telophase
spindle fibers break down, nuclear envelope reforms, nucleoli reappear
cytokinesis
in animal cells: actin filaments form a contractile ring, which pinches off the two daughter cells
functions of mitosis
development, growth, replacement, repair
Cancer Cells
have escaped cell cycle control
Two properties are required for cancer
uncontrolled growth and invasive ness
third property for cancer cells
ability to metastasize
origins of cancer
porto-oncogenes are turned on: become oncogenes, stimulate growth
tumor suppressors are turned off: growth control is lost
what are the other origins of cancer
DNA repai malfunction, telomerase activation