| "DNA polymerase adds nucleotides to a growing DNA strand, guided by the sequence of the template strand. The growing DNA strand is assembled in the 5' to 3' direction with the appropriate base pairs formed at each position. Incoming nucleotides are added to the free 3' hydroxyl group that is presented at the end of the growing strand. The 3' end of the growing strand is positioned in the active site of DNA polymerase. Catalysis is carried out by two highly-conserved aspartate residues and several crucial magnesium ions. The correct incoming nucleotide, deoxyCTP in this case, is selected by the next unpaired base on the template strand. The incoming nucleotide is added to the growing strand. A new covalent phosphodiester bond is formed that extends the length of the growing strand by one nucleotide. The polymerase moves down the DNA to the next unpaired base on the template strand, and the catalytic process is repeated." Essential Cell Biology, Second Edition by Alberts, Bray, Hopkin, Johnson, Lewis, Raff, Roberts, Walter copyright 2004 by Garland Science Publishing |
