Answer: Damage to DNA.
Step-by-step explanation:
The cell cycle is a serie of stages and events that take place in cells which allows them to divide and produce new cells through duplication of DNA and division of the cytoplasm.
The cycle consists of four phases:
- G1 phase: the time in which a cell grows.
- S phase: synthesis of DNA
- G2 phase: known as interphase, additional modifications occur in preparation for mitosis
- M phase: mitosis and cytokinesis
The g1 phase is the first of four phases of the cell cycle. In this stage, the cell synthesizes mRNA and proteins for the next steps. It is a growth phase, because it is the stage in which a cell grows.
A checkpoint is a point in the cell cycle at which the progression of a cell to the next stage in the cycle can be halted until conditions are favorable. So, if the cell is halted in G1 phase, is because something went wrong and the cell is not ready for the next step of the cycle.
The integrity of the DNA is assessed at the G1 checkpoint, and DNA damage is the main indication for a cell to restrict and not enter the cell cycle. If conditions are not adequate, the cell will not continue to the S phase of interphase.