Cell Cycleinished

What are the three major checkpoints

• G1

• G2/M

• Metaphase to anaphase

What happens in the starts (G1) checkpoint

Cell commits to cell-cycle entry and chromosome duplication

What happens in G2/M checkpoint

Early mitotic events with chromosome alignment on the spindle occur

What happens in the metaphase to anaphase checkpoint

Sister chromatids separate, anaphase triggered

Cyclins

Proteins that activate the Cdks to do their things

How are cyclins activated

By specific cues such as cell size or intra/extracellular signals such as growth factors, hormones

What are Cdk

Protein enzymes that add phosphates to various proteins involved in cell cycling

What does APC/C stand for

Cyclops one or anaphase promoting complex

What is the APC/C

A ubiquitin ligase that catalyzes the destruction of major proteins: securin and S- M-cyclins

Securin

Protects protein links between sister chromatids and unleashes anaphase

Why is APC/C important

Required for completing of the mitosis and the beginning of cytokinesis

G1/S cyclins

Activate Cdks in late G1 to trigger progression through the restriction point (commits)

S-cyclins

Bind Cdks to help stimulate chromosome replication and control early mitosis

M-cyclins

Activate Cdks that stimulate entry to mitosis

What govern activities of G1/S cyclins

Cyclin D

G1 cyclin

Cyclin E

G1/S cyclin

Cyclin A

S cyclin

Cyclin B

M cyclin

What are ORCs

Initiator proteins

Why must genome be copied only once during the cycle

To avoid gene amplification