The copying of the DNA molecule is a fairly reliable process. As new nucleotides are added, there is an error rate of about 1 in .... base pairs. The enzyme, .... proofreads the new strand and looks for errors. If a mistake is found, this same enzyme removes the erroneous .... and replaces it with another. After the proofreading, there is a final error rate of only 1 in .... base pairs.

The copying of the DNA molecule is a fairly reliable process. As new nucleotides are added, there is an error rate of about 1 in1,000,000 base pairs. The enzyme, DNA polymerase proofreads the new strand and looks for errors. If a mistake is found, this same enzyme removes the erroneous nucleotide and replaces it with another. After the proofreading, there is a final error rate of only 1 in10 billion base pairs.