Cell Cycle Power Point

The Cell Cycle  Biology 1 CP (Spring ’08)



The Cell Cycle describes the life of a eukaryotic cell  they

have a nucleus

Life of a eukaryotic cell is shown in a cycle.  Cell Cycle  a repeating sequence of cellular growth and division. 

Stages of the Cell Cycle Consists of 5 stages  Three of the stages together are called Interphase. 

 These

include G1, , S, & G2

Interphase 1. G1 (First growth phase)  Cell

grows rapidly  Occupies major portion of the cell’s life

2. S (Synthesis phase)  DNA

is copied  Each chromosome consists of two chromatids attached at the centromere.

3. G2 (Second Growth Phase)  Preparations

are made for the nucleus to

divide.  Microtubules are assembled  (hollow protein fibers -- move chromosomes during mitosis)

The other 2 phases 4. Mitosis – the process during cell division in which the nucleus of a cell is divided into two nuclei. (Makes an identical copy of another cell) 5. Cytokinesis – “…” in which the cytoplasm divides.

How do cells know when to divide?



Cells have “Checkpoints”  “red



light, green light”

1. Cell growth checkpoint (G1):  If

conditions are good, moves on to S phase  If conditions are not favorable, the cell cycle will stop.

2. DNA Synthesis (G2) checkpoint  DNA

replication checked by repair enzymes  If passed, the proteins help trigger mitosis.

3. Mitosis checkpoint - If passed, then moves on to G1 phase.