Question

List the steps of error correction sequence for newly replicated DNA why is this sequence important which molecule acts as the proofreader?

Answer 1

DNA polymerases ensure fidelity during DNA replication through proofreading to minimize mutations. If an incorrect base is added, DNA polymerase rectifies it with its 3' exonuclease action by removing the wrong nucleotide and then inserting the correct one.

Step-by-step explanation:

The sequence of steps for error correction in newly replicated DNA involves several repair mechanisms to minimize the number of mutations that persist. The key enzyme responsible for this process is DNA polymerase, which has a proofreading function.

1. DNA polymerase adds nucleotides to the new strand in a 5' to 3' direction, matching them with the complementary bases on the template strand.
2. If an incorrect nucleotide is inserted, the DNA polymerase's proofreading ability initiates. It checks whether the newly added base has paired correctly with the base in the template strand.
3. If an incorrect base is detected, the enzyme makes a cut at the phosphodiester bond and releases the wrong nucleotide through its 3' exonuclease action.
4. After the incorrect nucleotide has been removed, DNA polymerase can then add the correct nucleotide.

This proofreading process is crucial because if errors are not corrected, they may lead to more permanent damage, such as mutations that could contribute to diseases like cancer. In instances where proofreading fails, another mechanism called mismatch repair comes into play after replication to fix any remaining errors.