The 46 human chromosomes from one human cell contain about 3 billion base pairs. explain how this information is copied, seldom making any mistakes.

DNA is replicated by polymerase II enzyme in eukaryotes. The enzyme adds nucleotides complementary to the leading strand and then to an RNA strand that initiates the replication.
When the 3' _ >5' exonuclease finds a mismatched complementary pair, it nicks and excises the bases. The polymerase II then matches the right base pair and continues with replication.