Final answer:
The proteins that monitor genome integrity and prevent cell cycle progression are Rb, p53, and p21. These proteins act at the G1 checkpoint and detect damaged DNA, halting the cell cycle and triggering repair or cell death if necessary.
Step-by-step explanation:
The proteins that monitor the integrity of the genome and prevent a cell from progressing through a certain point in the cell cycle are the retinoblastoma protein (Rb), p53, and p21.
These proteins primarily act at the G1 checkpoint. p53 is a multi-functional protein that detects damaged DNA in cells during the preparatory processes of G1. If damaged DNA is detected, p53 halts the cell cycle and recruits enzymes to repair the DNA. If the DNA cannot be repaired, p53 can trigger apoptosis, or cell death, to prevent the duplication of damaged chromosomes. As p53 levels rise, the production of p21 is triggered. p21 enforces the halt in the cycle dictated by p53 by binding to and inhibiting the activity of the Cdk/cyclin complexes.
These regulatory proteins play a crucial role in maintaining genome integrity and preventing the progression of damaged cells through the cell cycle.