DNA replication occurs during interphase. The DNA must be copied in preparation for cell division (mitosis and meiosis). Specialized cells like muscle and nerve cells do NOT divide and therefore do NOT replicate their DNA.

Enzymes breaks the bonds between conjugate bases (A-T or G-C). This results in two single strands of DNA.

The enzyme, DNA Polymerase, travels along each single strand, adding a complementary nucleotide to the nucleotide on the parent strand.

This type of replication is semi-conservative.

The two identical strands are then attached by their centromeres(middle of the chromosome body) and they remain attached until early anaphase in mitosis or meiosis II.