Final answer:
The p53 protein at the G₁ checkpoint affects DNA binding by either repairing the DNA or triggering cell death if the damage is irreversible.
Step-by-step explanation:
The p53 protein primarily affects DNA binding at the G₁ checkpoint when there is damaged DNA in cells undergoing preparatory processes. 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.
Therefore, in the context of DNA binding, p53 functions to repair the DNA or eliminate the damaged cell altogether.