The document discusses the process of DNA replication in cells. It begins by reviewing that DNA is found in the nucleus and stores the cell's genetic information. It then describes in three steps how DNA replicates: 1) The DNA helicase enzyme unwinds the double helix, 2) DNA polymerase adds complementary nucleotides to each strand, and 3) DNA ligase seals the phosphate backbone. The document emphasizes that DNA replication is essential for cells to divide and for organisms to grow and develop.