Download MITOSIS NOTES

NOTES – CELL CYCLE
A. Cell Cycle
1. Consists of multiple “phases”: interphase (G1, S, G2) , and M phase (mitosis &
cytokinesis)
B. Interphase
1. Consists of G1 phase, S phase, and G2 phase
a. G1 phase – basic cell growth
b. S phase – DNA synthesis (once started, cycle is typically completed)
c. G2 phase – cell prepares for mitosis
C. M phase (also known as mitosis)
1. Consists of prophase, metaphase, anaphase, and telophase
a. Prophase - The chromosomes become thicker (chromatids) and you can see
them in a microscope. The nuclear membrane begins to disappear. Centrioles start to
move to opposite ends of the cell. Spindles attach near the centromere.
b. Metaphase - The choromosomes line up in the middle of the cell. Spindle
fibers, at each end of the poles, attach to the centromere.
c. Anaphase - The chromosomes pull apart and move to opposite poles. The
spindle fibers pull the chromosomes. Centromere splits for this to occur. Anaphase ends
when the chromosomes stop moving.
d. Telophase - The nuclear membrane reforms and the chromosomes disperse
(back to chromatin). Spindles break apart. Nucleolus becomes visible. Mitosis is
complete, but cell division is not complete.
D. Cytokinesis
1. Usually occurs at the same time as telophase. In animal cells, the cell membrane
draws towards the middle and the cell pinches into two almost equal daughter cells. In plant
cells, the cell plate forms midway between the new nuclei. This plate develops into a separating
membrane and the cell wall appears in the cell plate.
VOCABULARY YOU HAVE TO KEEP STRAIGHT
CENTROSOME – Two centrioles together. Called this during interphase
CENTRIOLES – Two small rod shaped structures, only in animal cells. Play a role in cell division.
CHROMATIN – When chromosomes appear as thin, threadlike coils
CHROMATID – When chromosomes shorten and thicken, and become dark and visible
CENTROMERE – A button like structure that holds the two sister chromatids together
SPINDLE FIBERS (OR SPINDLE) – fanlike microtubule structure that helps separate chromosomes.
CHROMOSOME – Two chromatids attached by a centromere
CYCLINS – Proteins that regulate the timing of the cell cycle
G1 phase
M phase
S phase
G2 phase