Formation of a 3'-5' phosphodiester
bond in DNA synthesis
During DNA synthesis, new nucleotides are added to the existing 3' end, by a 3'-5' phosphodiester bond (R - O - P - O - R). The original 5' end remains unmodified. Polynucleotides thus "grow" at the 3' end, in the 5'3' direction. Nucleic acid biochemical processes occur only in the 5'3' direction.
Figure © 2000 by Griffiths et al. ; text © 2007 by Steven M. Carr