iGen3 03-03smc

DNA chains grow in the 5' 3' direction only

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, and the polynucleotide "grows" by modification of the 3' end, in the 5'3' direction. Biochemical syntheses of nucleic acids occur only in the 5'3' direction.

Do not try to understand this process in any other way!

Figure © 2010 PJ Russell, iGenetics 3rd ed.; all text material © 2011 by Steven M. Carr