Question

Explain what factors would cause a cell to stop at each of the 3 cell cycle checkpoints

Answer 1

Answer and Explanation:

Cyclins and cyclin-dependent protein kinases (CDPKs, cell proteins) also function to control the cell cycle. A group of cyclins: the G1 cyclins, are synthesized during G1 phase and function to activate CDPKs which initiate DNA synthesis at the G1/S checkpoint. The cell fails to progress to S phase if there is no sufficient synthesis of G1 cyclins. After a cell passes through this point, the G1 cyclins are degraded, allowing for another group of cyclins: the M cyclins (mitotic cyclins) to be synthesized. M cyclins activate a second group of CDPKs which allow the cell to pass the G2/M control point and into mitosis.

In the G1/s check point, entrance into the S phase is blocked if the genome is damaged. In the G2/M check point, entrance into the M phase is halted if the DNA replication is incomplete. In the M phase, anaphase blocked if chromatids are not properly assembled.