Explain how DNA is replicated within the cell.

DNA is replicated within the nucleus of the cell through a process called semi-conservative replication. The first part of the process involves the splitting of the double stranded molecule into two separate strands. This is catalysed by the enzyme DNA helicase which breaks the (hydrogen) bonds between the bases of each nucleotide. For each strand to then be replicated to produce two double-helix molecules, a primer must bind to each strand. Once a primer has bound to each strand, replication can begin.Free DNA nucleotides within the nucleus are then attracted to their complimentary exposed bases on each strand (A to T, C to G). These new bases form (hydrogen) bonds with the existing bases and create two double stranded molecules. The final step in the process involves the formation of the backbone that runs along the edge of the new molecules where the new bases have paired up. DNA polymerase is the enzyme involved in producing these bonds. There are now 2 identical molecules of double stranded DNA, each containing 1 strand from the original molecule.