Consider two fragments of DNA of radius r₁ = 30 nm and r₂ = 35 nm when they are coiled up as they move through a gel. An electrophoresis analysis (Fig. 17.38) is carried out to separate these two fragments. Suppose the drag factor C in Equation 17.19 is C = 5.0 ? 10^-5 kg/(m ? s), and assume each fragment has a charge q = -10e.?

(a) If the electric field has a magnitude of 1.0 N/C, what is the speed of each fragment in the gel??

(b) How long will it take the smaller fragment to move a distance 1 cm (a typical distance used in DNA fingerprinting)??

(c) After the time in part (b) has elapsed, what is the separation of the two different size fragments in the electrophoresis tube?

Figure P17.38

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