Check Points of Cell Cycle

Identify and describe the Four Cell Cycle Checkpoints; describe what determines whether cells will continue with events or stop events at the checkpoints

G1 Checkpoint- This is the first cell-cycle checkpoint and it occurs late in the G1 cycle. This cycle determines whether the cell will continue through the cycle and divide, or exit the cycle and enter G0. To pass, it has to be big enough, it has to have enough nutrients, it has to receive a social signal to continue, and it has to have undamaged DNA. ( If DNA is damaged, the protein p53 activates genes that will either stop the cycle until the DNA is repaired, or cause the cell to destruct.) (because p53 prevents damaged genes from continuing through the cycle it is known as a tumor suppressor.)

G2 Checkpoint - This checkpoint is at the boundary between G2 and M phase. If DNA or chromosomes are damaged or not copied correctly or the cell isn’t the correct size, MFP is blocked from turning on, and the cell remains in G2 phase.

M-Phase Checkpoints (2 of them) -

1) The first of the M-phase checkpoints regulates the onset of anaphase. This checkpoint makes sure that all kinetochores are attached properly to the spindle apparatus, so that chromatids will be separated correctly.

2) The second checkpoint occurs before M phase enters back into G1. If the chromosomes didn’t separate correctly, cyclins won’t be destructed, and the activity of MPF will keep the cell arrested in M phase. The cell will not undergo cytokinesis, and it won’t exit M phase.

Explain what Social Controls on the cell cycle are, and what type of organisms would exhibit social controls over the cell cycle

Social control is when, in a multicellular organism, cells divide only when signals from other cells tell them to. This way, individual cells only replicate when its in the best interest of the whole organism. Social controls determine whether a cell will continue past the G1 checkpoint.

Cells can become cancerous when cells...