Final answer:
In DNA replication, the RNA primer on the leading strand is removed by DNA polymerase I, which also fills the resulting gaps with DNA nucleotides. DNA ligase then seals these nicks, maintaining the integrity of the DNA strand.
Step-by-step explanation:
The replacement of the primer by new dNTPs on the leading strand involves several key steps in DNA replication. As the replication fork moves, DNA polymerase adds nucleotides in a 5' to 3' direction on the leading strand using a single RNA primer. When the RNA primer is no longer needed, it is removed by the exonuclease activity of DNA polymerase I. This polymerase then fills in the gaps with DNA nucleotides. Finally, DNA ligase seals the nicks in the DNA strand, completing the process and ensuring a continuous double helix is formed.