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Terms in this set (28)

* to go through each stage you need to pass checkpoints. to pass checkpoints, you need cyclin complexes present to inhibit proteins that otherwise will inhibit cell replication!

G0- Resting. Cell left cycle and stopped dividing. Cyclin C-CDK3

- G1: growth phase. cell increases protein supple and organelles, cell grows in size.
CHECKPOINT = restriction point; the cell becomes committed to entering cell cycle. DNA damage or defects can halt cell cycle in G1. Cyclin D is bound to CDK4 or CDK6 and Cyclin E is bound to CDK2. These complexes phosphorylates Rb (tumor suppressor protein made from tumor suppressor genes like p53), and Rb cant inhibit DNA replication.
**Inhibitors of Cyclin D and E: KIP/CIP inhibitors such as p21, p25, p57
**Inhibitors of Cyclin D only: INK inhibitors such as p15, p16, p18, p19
CANCER: Defective checkpoint due to p53 mutation (p53 can no longer suppress cell cycle), no apoptosis or cell death.

- S phase: Chromosomes replicated, DNA doubled. Completed ASAP bc exposed base pairs are sensitive to harmful factors. Cyclin A-CDK2 (activates DNA replication)

- G2: Cell continues to grow. G2/M
CHECKPOINT = DNA damage checkpoint, checks that all went well. CHECKPOINT- mitosis checkpoint, checks if mitosis is complete Cyclin A- CDK1 and Cyclin A-CDK2 complexes activates mitosis!

Mitosis (M phase): prophase, metaphase, anaphase, telophase, cytokinesis
CHECKPOINT- mitosis checkpoint, checks if mitosis is complete Cyclin B-CDK1

*The cyclins keep the cell cycle going, CDK inhibitors are what stop it when somethings wrong.

(COMBOT- memorize cdk and inhibitors as well)