Help please :) (B) Now consider a situation where a DNA polymerase enzyme is rep
ID: 140914 • Letter: H
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Help please :)
(B) Now consider a situation where a DNA polymerase enzyme is replicating one strand of DNA. The polymerase is fixed in space, and cannot rotate or translate. This is not uncommon in cells, where the ends of the DNA are fixed, as is the polymerase machinery. As a consequence, the DNA within it cannot rotate as it is extruded out of the polymerase. The other end of the double helical DNA is fixed, and the DNA to the left of the polymerase is entirely double helical. no rotation allowed newly synthesized DNA fixed single- stranded DNA double-helical DNA DNA polymerase (fixed) Answer the following questions about the state of the double helical DNA as the replication progresses, assuming that the DNA adopts a minimum energy conformation, given the topological constraints. 0) Will the twist, T, of the double-helical DNA to the left of the polymerase increase, decrease, or stay the same as the DNA polymerase progresses? Explain your answer (ii) Will the linking number, L, of increase, decrease, or stay the same? Explain. (ii) Will the writhe, W, increase, decrease, or stay the same? Explain.Explanation / Answer
(1) will the twist T of the double helical DNA to the left of the polymerase increase,decrease, or stays as the DNA polymerase progresses.
Twist is simply the number of helical turns of one strand about the other, that is the number of helical turns of one strand about the other,that is the number of times one strand completely wraps around the other strand. The lenght and the pitch of the DNA in the solution determines the twist.So if the lenght of DNA strand increase by help of DNA polymerase the twist also will increase.calculated by the following formula.
Tw = length (base pair,) / pitch ( bp ,/ turn).
(2) Will the linking number Lk of increase, decrease or stay the same.explain.
Sum of two geometric components called twist and writhe.
Lk= Tw+Wr.
Linking number will remain the same . The linking number does not change even when the DNA is forced to lie in a plane in a stress confirmation or wheather it is allowed to supercoil or left freely in space . The linking number remains the same.
(3) Will the writhe Tw increase,dec decre or remains same. Explain.
The number of times that the DNA helix is coiled about itself in 3D space is called writhe.
Wr= Lk - Tw
Unlike linking number and twist the writhe of the DNA depends on the path the helix axis takes in space and not on the fact that DNA has two strands. The path of the DNA is present on a plane writhe will remain zero that means it will remain same.
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