What stops DNA from making errors when it copies itself

Answer;

DNA polymerase

Explanation; DNA polymerase is the enzyme that catalyzes the process of DNA replication in which DNA copies itself. DNA replication is a highly accurate process, however, mistakes may occasionally occur for example, when a DNA polymerase inserts a wrong base. Uncorrected mistakes during replication are dangerous and may sometimes lead to serious consequences, such as cancer. Most mistakes during the process of replication are corrected by DNA polymerase during replication or by post-replication repair mechanisms.