Text 6. DNA Replication

DNA replication is a very complex process during which mistakes happen. Uncorrected mistakes may lead to harmful mutations. In the living cell, errors are kept to a very low frequency (about one in 10⁹) by a number of repair mechanisms. One such mechanism is mismatchrepair.This is carried out by the enzyme DNA polymerase which 'proofreads' newly formed DNA against its template as soon as it is added to the strand. If it finds an incorrectly paired nucleotide, the polymerase reverses its direction of movement, removes the incorrect nucleotide, and replaces it before replication continues. The process is similar to correcting a typing error by going back a space, deleting the error, and typing in the correct letter before continuing.