When scientists mutate bacteria or even embryos of lambs and other animals, why doesn't the p53 reverse whatever mutation the scientists cause? I know that the p53 stops the DNA from mutating and since the restriction enzymes essentially mutate the DNA, why doesn't the p53 stop it? Does the p53 gene have to be temporarily turned off?
I am no expert in this area, and this answer is only based on a reading of the Wikipedia article on p53, which you should perhaps have read carefully. I welcome edits or correction by persons more knowledgeable than me on this topic.
First, although the Wikipedia article neglects to mention it, you can forget about bacteria as the protein is only found in eukaryotes.
Second, one needs to consider what exactly p53 does in relation to protection of DNA from mutation, how it is activated to do this, and hence whether this would occur in the circumstances of the introduction of mutated DNA into a eukaryotic genome.
From the article it appears that “It (p53) can activate DNA repair proteins when DNA has sustained damage”, and that “p53 becomes activated in response to… stressors, including… DNA damage (induced by either UV, IR, or chemical agents such as hydrogen peroxide)…”
The manipulation of animal DNA will be performed outside of the target organism, and the modified DNA re-introduced into the genome by one of several mechanisms that are unlikely to evoke the stress signals that are evoked by agents that damage DNA ‘naturally’. Hence there is no reason to expect the activation and action of p53 in response to this type of experiment.