cell cycle power point
TRANSCRIPT
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 rapidlyOccupies major portion of the cell’s life
2. S (Synthesis phase)DNA is copiedEach 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) checkpointDNA replication checked by repair enzymes If passed, the proteins help trigger mitosis.
3. Mitosis checkpoint
- If passed, then moves on to G1 phase.