1. MODIFIED from a slide show by Kim Foglia

4. INTERPHASE = G1, S, G2
G2- Gap 2 Grow Produce molecules & organelles needed for cell division
MITOSIS
G1- Gap 1 Grow by producing proteins & organelles
G0- Cell leaves cycle
and stops dividing Most body cells in this phase
S- Synthesis
DNA replication
Some can return to cycle with signal (Ex; Liver cells respond to injury) Some never divide again (Ex: Mature nerve, muscle cells)

10. Cyclin-dependent kinases (Cdk’s) are present all the time but inactive unless combined with cyclins
Enzymes that work by adding a
phosphate group
to other molecules
Presence of MPF triggers passage past G1 & G 2 checkpoints

11. Cyclin levels
change throughout
cell cycle
Fluctuating levels
of different
Cyclin-Cdk complexes seem to control
all stages of
cell cycle

15. Telomeres protect DNA from being degraded
Telomeres become shorter with each replication; shorter in older cells
Telomerase enzyme lengthens telomeres
Cancer cells have increased telomerase activity
2009 Nobel Prize Physiology/Medicine
Discovery of Telomeres
Jack Szostak Carol Greider Elizabeth Blackburn.

16. Most cells divide 20-50 times in culture; then stop, age, die
Cancer cells are “immortal” -HeLa cells from a tumor removed from a woman (Henrietta Lacks) in 1951 are still reproducing in culture

17. CANCER CELLS Don’t respond to control signals
Lose density-dependent inhibition
Lose anchorage dependence
Telomerase enzymes maintain/replace telomeres
Transformation-
process that changes
a normal cell into
a cancer cell