Why does dna replicate from 5 to 3

Stage two - Leading strand is synthesised continuously. Stage two - Lagging strand is synthesised in fragments. Stage two - Fragments are sealed together by ligase. Stage three - Strands twist to form double helix. Leading strand is synthesised continuously. This would mean that the triphosphate providing the energy for addition of a new nucleotide would be on the DNA strand that is extended, and not on the newly added nucleotide.

One disadvantage of this approach is that nucleotide triphosphates spontaneously hydrolyze under aqeuous conditions. This is no significant problem for the 5'-3' polymerase, as the triphosphate is on the new nucleotide and the polymerase just has to find a new nucleotide. For the 3'-5' polymerase spontaneous hydrolysis is a problem because the triphosphate is on the growing chain.

If that one gets hydrolyzed, the whole polymerization needs to be either aborted or the triphosphate need to be readded by some mechanism. Mansfield for more information about this. They created a model on early polymerase evolution, though they don't reach any final conclusion.

In my opinion, Prof. Allen Gathman's "great minutes video on Youtube" is a pretty waste of time if you already know how hydrolysis happens. In the usual case, the triphosphate which is hydrolysed belongs to the added nucleotide, while in the latter case, the triphosphate which is hydrolysed belongs to the nucleotide on the growing strand. Both are feasible.

In fact, it is known that RNA polymerase has dual activity, but you see, RNA polymerase doesn't have proofreading activity!. Why it is so, would need a lot more explanation if in words but I think a picture has far better explanatory power than a thousand words. The other important consideration is repair.

If one or more nucleotide is missing in one strand, repair of the missing nucleotide would be impossible for 3' to 5' synthesis, because no 5'-triphosphate is present. On the other hand, 5' to 3' synthesis does not require a 3'-triphosphate present at the repair site. This is important. Citation: Pray, L.

Nature Education 1 1 Arthur Kornberg compared DNA to a tape recording of instructions that can be copied over and over. How do cells make these near-perfect copies, and does the process ever vary? Aa Aa Aa. Initiation and Unwinding. Primer Synthesis. The Challenges of Eukaryotic Replication. References and Recommended Reading Annunziato, A. Journal of Biological Chemistry , — Bessman, M. Journal of Biological Chemistry , — Kornberg, A. Science , — Lehman, I. Journal of Biological Chemistry , — Losick, R.

Science , — Mackiewicz, P. Nucleic Acids Research 32 , — Ogawa, T. Molecular and General Genetics , — Okazaki, R. Article History Close. Share Cancel. Revoke Cancel. Keywords Keywords for this Article. Save Cancel. Flag Inappropriate The Content is: Objectionable. Flag Content Cancel. Email your Friend. Submit Cancel.

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