Reptation Theory and the Gel-Electrophoresis of DNA

The idea is the following. Suppose you have a solution containing the bunch of DNA molecules that you wish to separate. Spread this solution 

Let s consider, for example, separating linear DNA chains of different lengths. Can we work out how the speed of electrophoretic motion depends on the chain length. At To get an idea, we will explore two limiting cases. 

First of all, suppose the electric field is very strong. We follow the front end of a DNA molecule which moves forward and creates new bits of the tube. This end will spend more time traveling along the field direction 

What a relief The two dependencies do not cancel out this time, and we find that the speed of the motion along the tube, vt, is  

How fast will the molecule s center of mass move Suppose the chain has crawled along the tube by a short distance A. The result of this motion is convenient to represent as if you chop a piece of length A at one end of the chain and stick it to the other end. When you chop the piece, you transport it by a distance The center of mass will move by a 

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