DNA molecule winds up. What is the shape of DNA? The nitrogen bases form the rungs of the ladder and are arranged in pairs, which are connected to each other by chemical bonds. What is DNA made of? DNA is made of chemical building blocks called nucleotides.
These building blocks are made of three parts: a phosphate group, a sugar group and one of four types of nitrogen bases. To form a strand of DNA, nucleotides are linked into chains, with the phosphate and sugar groups alternating. What does 5 to 3 direction mean? This linkage provides the sugar-phosphate backbone that gives DNA its structural rigidity.
What is the 5 to 3 direction? The 5' and 3' mean "five prime" and "three prime", which indicate the carbon numbers in the DNA's sugar backbone. The 5' carbon has a phosphate group attached to it and the 3' carbon a hydroxyl -OH group. This asymmetry gives a DNA strand a "direction". Is mRNA synthesized 5 to 3? The mRNA is single-stranded and therefore only contains three possible reading frames, of which only one is translated. What is the 5 prime end of DNA? Why can't DNA leave the nucleus?
Where rocks on opposite sides of a fault move in opposite directions or in the same direction at different rates? Two plates move past each other in the opposite directions?
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Where rocks on opposite sides of a fault move in opposite directions orin the same direction at a different rate of speed? If rocks on opposite sides of a fault move in opposite directions or in the same direction at different rates what kind of fault exists?
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Still have questions? Find more answers. Previously Viewed. Why do the two DNA polymerase enzymes move in opposite directions? Unanswered Questions. What are the advantage and disadvantages of the bandala system? What letter in the word Wilmington is the same number in the word counting from the beginning as it is in the alphabet? Are business terms exclusively for commercial transactions? The problem with this model is that ribonucleotide-3'-triphosphates are less stable under acidic conditions due to the neighbouring 2'-OH though this obviously only applies for RNA, not for DNA.
So any 3'-5' polymerase would likely need to use the same nucleotide-5'-triphosphates as the 5'-3' polymerase. 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. That is 3' to 5' synthesis does not allow nucleotide repair. Actually there is a polymerase that catalyzes 3' - 5' elongation. See for example the Thg1 superfamily. Sign up to join this community.
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