Question

DNA Electrophoresis:

Our Gel: Information about the gel in Figure 1: • Run Time: 105 minutes. • The DNA sample contained 13 different sizes of DNA molecules (Table 1). The apparatus delivered a potential difference of 80 Volts across the gel. The distance between the electrodes was 19 cm. • This Voltage difference creates an electric field of 421 V/m (421 N/C)

a) The DNA reaches terminal velocity quickly during electrophoresis and stays in that state. Solve for the terminal velocity for the viscous and drag force case.

b) Which of these terminal velocities depend on the size of the DNA molecule? How does the terminal velocity change with molecule size? ( does terminal velocity go up or down as the size gets bigger?)

c) Based on your calculations is the resistive force on a DNA molecule during electrophoresis best represented by the viscous or drag model?

Answer 1

a) Terminal velocity is the maximum velocity attainable by an object. The more viscous a liquid or the less it want to flow, the more restraining force will be exerted thus reducing the terminal velocity

Drag force is resistance force caused by the motion of body through fluid.Terminal velocity falls through a fluid when the drag force is equal to force of gravity acting on the object.

b) Drag force depend on size of DNA molecule. Heavier objects will have higher terminal velocity than light objects

c) viscous drag force is responsible for resistance