Which enzyme is not working correctly if the dna had more than nomal level of mutations?

The name of the enzyme is DNA POLYMERASE.

Explanation:

DNA replication is the process by which the DNA reproduce itself. During the process of replication, the blocks of nucleotide that are been added are checked constantly by mean of proof reading in order to ensure that all the nucleotide are properly paired. The enzyme that carried out the work of proofreading and subsequent repair is DNA polymerase enzymes. The activities of the enzyme ensures that no mutation occur in the DNA strands that are been produced.