Cell Cycle Notes
Cell Cycle- repeating sequence of cellular growth and division
during the life cycle of an organism
Interphase- first 3 phases of the cell cycle (90% of cells time will
be spent here)
1. First growth (G1) phase-
-cells grow rapidly
-cell not dividing remain here
-cells carry out routine functions
-occupies major portion of cells life
2. Synthesis (S) phase-
-DNA in cell is copied
-at the end of this phase chromosomes
have two chromatids with a centromere
3. Second Growth (G2) phase-
-preparations are made for the nucleus to divide
-hollow protein fibers (microtublules) are rearranged preparing for
-process during cell division that the cells nucleus will divide into
-each nucleus will have the same # and kind of chromosomes as the
-process of cell division when the cytoplasm will divide.
Control of the Cell Cycle
"Red light- green light"
How do cells know when to divide?
-control system that controls
the phases of the cell
What happens if the control is
Cancer- uncontrollable cell growth
1. Cell Growth (G1) checkpoint-
-makes the decision to whether the cells will divide
-will divide if the cell is large and healthy enough.
-then will move on to the (S) phase
2. DNA synthesis (G2) checkpoint-
-DNA replication is checked, if all looks good then mitosis can begin.
3. Mitosis checkpoint-
-triggers the exit from mitosis.
-signals the beginning of the G1 phase. (major growth phase)
Assignment: Ch. 6 section 2
-end of section questions on page 127 (#1-4)
-"Exploring Further" on page 127 (read)
answer the following:
1. Where in the cell cycle could scientists target anticancer
2. What type of environmental factors have been associated
with the onset of cancer?