Why Does DNA Polymerase Only Add Nucleotides to 3‘ OH?
: Why Does DNA Polymerase Only Add Nucleotides to 3‘ OH? A triphosphate is required to provide energy for the bond between a newly attached nucleotide and the growing DNA strand. However, this triphosphate is very unstable and can easily break into a monophosphate and an inorganic pyrophosphate, which floats away into cell. Why Does DNA Polymerase Only Add Nucleotides to 3′? : Why Does DNA Polymerase Only Add Nucleotides to 3′? At the 5′ end of the DNA, this triphosphate can easily break. If a strand has been sitting in the cell for a while, it would not be able to attach new nucleotides to the 5′ end once the phosphate had broken off. The 3′ end only has a hydroxyl group, so as long as new nucleotide triphosphate are always brought by DNA polymerase, synthesis of a new strand can continue no matter how long the 3′ end has remained free. This Presents a Problem: This Presents a Problem One strand of the double helix is 5′ to 3′ and the other one is 3′ to 5′. How can DNA polymerase synt