Question

A safety device that operates in mammalian cells to restrain them from entering S phase with damaged DNA depends on a protein called _______________, which accumulates in the cell in response to DNA damage and halts the cell-cycle control system in G1.

Answer 1

Step-by-step explanation:

Cell cycle control

The eukaryotic cell cycle has 4 major phases namely G1 , S, G2 and M phase. G1, S and G2 form the Interphase or the preparatory phase and M phase is the actual phase of cell division. Entire cell cycle is regulated by 3 major checkpoints which restrict the passage to the next phase if their is any defect in the previous phase.

When a damaged DNA is detected then a protein called p53 is activated by sensory proteins ATM and Chk. These sensory proteins activate already present p53 by not letting it bind to its inhibitor Mdm2. This results in increased concentration of p53 in the cell and also activation of other proteins like p21, p27 etc. Finally they lead to the halt or stopping of the cell cycle control system.